Too many animals' _____ are disappearing.

The desert is a difficult _____ for people to live in.

Do _____ elephants join other elephant families?

The hurt elephant recovered _____ and soon returned to her family.

Some people believe animals live _____ in zoos, but I don't know about that.

If poachers aren't stopped, elephant populations will disappear _____.

If the Arctic ice continues to melt, _____.

Choose the correct sentence.

If people ______ the fish they eat carefully, they _____ the environment.

In the past, people rarely traveled _____ their own country.

Marco Polo ___ for Asia more than 700 years ago.

___ probably wasn't available in Europe before 1300.

Travel is easier now than in the past, but it is still _____ sometimes.

Were a lot of people _____ to travel by Marco Polo's book The Description of the World?

They _____ live in Bogotá.

Did travelers on the Silk Road use to _____ one another?

Did fewer people _____ travel overseas?

I _____ the Silk Road was only one road.

As a child, Magaly _____ to take the bus alone.

Last year, Spanish _____ by Mr. Sanchez.

The first book _____ in what year?

Before cars _____, people used to travel by horse and wagon.