During the tourist season, there are many people wandering in this city to see the old castles_____ in the sixteenth century.
| A．to be built | B．being built |
| C．having been built | D．built |
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 which is |
American women usually identify their best friend as someone _____ they can talk frequently.
| A．who | B．as | C．about which | D．with whom |
George Orwell, _______ was Eric Arthur, wrote many political novels and essays.
| A．the real name | B．what his real name | C．his real name | D．whose real name |
_______ get such a book?
| A．Where do you think can I | B．Do you think where can I |
| C．Do you think where I can | D．Where do you think I can |
Is this the reason _______ at the meeting for his carelessness in his work?
| A．he explained | B．what he explained | C．how he explained | D．why he explained |