1 . Spending a few hours learning about the history and culture of the destination will help tourists understand      they're seeing

A．what	B．where
C．that	D．why

2 . Tony couldn’t remember ______he had turned off the computer before he left the office．

A．that	B．where
C．when	D．whether

3 . The researchers have discovered __________they believe to be a new species.

A．which

B．who

C．where

D．what