Are eight hours of sleep enough for teenagers?

There are always more homework on weekends than we expect.

The books in my office is very valuable to me.

Unless there are a dramatic and comprehensive change in government policies soon, the economic conditions in that country will continue to worsen.

Studying a foreign language often lead students to learn about other cultures.

The news about the effects of air pollution on the development of children's lungs is disturbing.

Some of the works for my classes is pretty challenging.

A lot of the people in my class works during the day and attends class in the evening.

The audience is waiting for the show to begin.

One of the most common names for dogs in the United States are "Rover."

Mathematics is easy for me to understand, but physics is more difficult.

All of the windows in our house was broken in the earthquake.