FOR or SINCE

I've been part of the fossil research team ____ 3 months.

• for
• since

Jason hasn't written any research articles ____ he became a professor.

• for
• since

The museum has had the skeleton on display ____ 1998.

• for
• since

Penny has been a member of the Science Club ____ 2 years.

• for
• since

Archaeologists have known about the footprints in the cave ____ six months.

• for
• since

Researchers haven't discovered any fossils in the area ____ last year.

• for
• since