It is no use (a)   (regret) your past mistake.

She was elected a (a)   (product) worker.

He regretted (a)   (complete) his task in time.

Getting enough exercise is of great (a)   (necessary)

We need to have a close (a)   (relate) with each other.

A few minutes later the bomb went (a)   , destroying the vehicle

It is essential (a)   (wash) hands before having a meal.

A young man was found (a)   (beat) to death last night.

A national park is a  (a)   (protect) area where you can see animals and plants in their natural habitat.

Eggs are considered to be a kind of necessary and common food in our life. However, do you know when did people begin to eat eggs? It is said that people        1        （eat） eggs since about six million years ago.

(a)  

n about 7000 BC, people in China and India were keeping chickens and eating their eggs, so they didn't have to go        2        （hunt）for wild bird eggs anymore.

(a)  

All through the Middle Ages, chickens only laid eggs for part of the year,      3      （main）in spring.

(a)  

  4    this season, there is plenty of daylight but it isn't too hot.

(a)  

That's why the         5   (填）      （west） have Easter Eggs           6            （celebrate） the return of eggs in spring.

(a)  

That's why the         5         （west） have Easter Eggs           6 （）填_           （celebrate） the return of eggs in spring.

(a)