In many countries, people are living a “throwaway lifestyle”. Things are used for a short time and thrown away.

• In many nations today, people habitually use items for a short time and throw them away.

• In many nations today people habitually use items for a short time and throw them away.

• Recently in many nations, people are now in a "throwaway society". 

Answer explanation

A comma should be written after an introductory phrase like 'in many countries'.

Some people think that because children find subjects such as mathematics and philosophy difficult, they ought to be optional instead of compulsory.

• Some individuals opined that since children find some subjects like mathematics and philosophy hard to understand, they should be made optional instead of compulsory.
• Children nowadays find it difficult to understand subjects like mathematics and philosophy. Some people have therefore suggested that these subjects be made optional.
• Some children are finding it taxing to study mathematics and philosopy, and so they are suggesting that these subjects be made elective.

The global demand for oil and gas is increasing. Some people believe that we should therefore encourage the exploitation of remote areas.

• The demand in the global market for petroleum products has being on the increase, and some people believe that remote areas should be explored for oil.
• The demand for petroleum products has been on the increase; thus, some individuals have opined that remote areas be explored for petroleum.
• The demand for petroleum products has been on the increase, thus, some individuals have opined that, remote areas be explored for petroleum.

In many parts of the world, people are living longer.

• In many states worldwide, many people are living for long periods of time.
• Life expectations is on the rise in many countries worldwide.
• Life expectancy is increasing in many countries worldwide.
• Life expectancy has being increasing in many countries worldwide.

People in the current generation are not fit and active. This will cause health problems in the future.

• A lot of people today are not physically fit and active, and it is believed that this will result in health problems for them in the future.
• Most people today are sedentary in their lifestyle and it will cause lots of numerous problems for them in the future.
• A large proportion of individuals in many parts of the world today are unfit and inactive. This is capable of causing numerous health problems for them in the years to come.

Some scientists think that computers will soon become more intelligent than humans, and that this could be dangerous to society.

• A number of experts in the field of science and technology have opined that in a few years from now, computers wil become more intelligent than humans, and this could be risky to the society.
• Some scientists have suggested that screen gadgets will soon become more wiser than human beings, and this could cause a lot of danger to human life and to our world.
• A few scientist have expressed concerns about the risk posed by technology, as it is likely that computers will soon become smarter than human beings.

Some people believe that having more money will make them happier. Others argue that there are other factors that contribute to happiness.

• Some individuals believed that, being rich will make them happier. Other people however hold contrary opinion; they say that, there are many other factors that contribute to happiness.
• Some individuals hold the view that being rich will make them happier. Other people however hold a contrary opinion; they say that there are many other factors that contribute to happiness.
• Some individual hold the views that having lots of money will make them happier. Other people however hold a contrary opinion; they say that there are many other factors that contribute to happiness.

Experts say older people were happier and healthier in the past because they did more exercise and spent more time with family and friends, whereas many now suffer from loneliness and health problems.

• Experts in some parts of the world say that, the elders are happier and healthier in the past and this is because, they exercised more regularly and they spent more time with their friends and relatives, but elderly people today are lonely and they suffer more health challenges.
• According to experts, elderly individuals in the past were happier and healthier because they exercised more regularly and they spent more time with their friends and relatives, but elderly people today are lonely because they suffer more health challenges.
• Experts in some parts of the world say that elderly individuals were happier and healthier in the past due to the fact that they exercised more regularly and they spent more time with their friends and relatives, but elderly people today are lonely and they suffer more health challenges.

Different cultures are mixing today and the world is becoming a global village.

• Individual from different cultural backgrounds find it easy to interact with one another in recent times, and the world is becoming a global village.
• People from different tribe and tongue now finds it easy to interact with one another in recent times, and the world is becoming a global village.
• Individuals from different cultural backgrounds find it easy to interact with one another nowadays, and the world is becoming a global village.

Today more people are overweight than ever before.

• In recent times, people are overweight than ever before.
• These days, more inidividuals are overweight than ever before.
• The number of overweight individuals has increased in many parts of the world.