It is well-known to us all that knowledge is __ treasure, but practice is ___ key to it.
| A．a, ∕ | B．a, the | C．the, the | D．∕ , the |
Alice received an invitation from her boss，__________ came as a surprise.
| A．it | B．that | C．which | D．he |
The school is divided into two semesters, the first of__________is September through December, and thesecond January through May.
| A．what | B．that | C．which | D．one |
My friend showed me round the town，__________wasvery kind of him.
| A．which | B．that | C．where | D．it |
Between the two parts of the con-cert is an interval，__________ the audience can buy ice-cream.
| A．when | B．where | C．that | D．which |
Mary was much kinder to Jack than she was to the others，__________，ofcourse, made all the others upset.
| A．who | B．which | C．what | D．that |