Helping and Main Verbs

These Asian hunters have been following game.
1. Yes
2. No
At the time Siberia and Alaska were not entirely separated by a body of water.
1. Yes
2. No
The hunters must have walked across the land to America.
1. Yes
2. No
People must have been living in America for thousands of years.
1. Yes
2. No
The first inhabitants had probably come from Asia.
1. Yes
2. No
Water has not always separated Asia and North America.
1. Yes
2. No
In fact, the two continents were joined by a bridge of land and ice.
1. Yes
2. No
The ancestors of today's native Americans may have crossed this land bridge during a hunt.
1. Yes
2. No