Last Monday, I bought a second-hand computer, ______ was very slow.
| A．which price | B．its price | C．the price of whose | D．the price of which |
It is not always easy for the public to see _______ use a new invention can be of to human life.
| A．whose | B．which | C．that | D．what |
He dressed up and went to the party as if ________.
| A．was invited | B．had been invited | C．to be invited | D．invited |
After completing and signing it, please return the form to us in the envelope _______.
| A．provided | B．providing | C．having provided | D．provide |
The book was written in 1946, _______ the education system has witnessed great changes.
| A．since then | B．when | C．since when | D．during which |
He ______ be sitting at the gate, waiting for his lost son.
| A．used to | B．was used to | C．could | D．was accustomed |