Why did travel (a)   be so challenging in the past?

In the past, there didn't (a)   be as many opportunities for trade as there are nowadays

How did people (a)   buy things before money existed?

Before trade in China began, people didn't (a)   wear silk clothes.

Not too many people (a)   (live) in the cities.

Salaries (a)   (be) much lower.

People (a)   (not eat) so much processed food; their diet was healthier.

People (a)   (write) letters because they didn't have computers.

Families (a)   (be) closer and more connected than they are today.