The teacher asked the students to do the experiment __________ small groups.
| A．to | B．for | C．on | D．in |
I saw some trees the leaves of _____ were black with disease.
| A．that | B．which | C．it | D．what |
Their problem today is somewhat similar to _____ they faced many years ago.
| A．that | B．which | C．that which | D．it |
Dorothy was always speaking highly of her role in the play, ____, of course, made the others unhappy.
| A．who | B．which | C．this | D．what |
He made another wonderful discovery, ______ of great importance to science.
| A．which I think is | B．which I think it is | C．which I think it | D．I think is |
He’s got himself into a dangerous situation _____ he is likely to lose control over the plane.
| A．where | B．which | C．while | D．why |