b) Model: Scientists study a wide variety of subjects.

Do scientists study a wide variety of subjects? --- Yes, they do.

Scientists study a wide variety of subjects, don't they? -

Yes, they do.

1. Some scientists search for clues to the origin of the universe.

Do some scientists search for clues to the origin of the universe?--- Yes, they do.

Some scientists search for clues to the origin of the universe, don't they? -

Yes, they do.

2. Scientists examine the structure of the cells of living plants and animals.

Do scientists examine the structure of the cells of living plants and animals?--- Yes, they do.

Scientists examine the structure of the cells of living plants and animals, don't they? -

Yes, they do.

3. Other researchers investigate why we act the way we do.

Do other researchers investigate why we act the way we do?--- Yes, they do.

Other researchers investigate why we act the way we do, don't they? -

Yes, they do.

4. They solve complicated mathematical problems.

Do they solve complicated mathematical problems?--- Yes, they do.

They solve complicated mathematical problems, don't they? -

Yes, they do.

5. Scientists use systematic methods of study.

Do scientists use systematic methods of study?--- Yes, they do.

Scientists use systematic methods of study, don't they? -

Yes, they do.