We will fail the exam____we study hard．
That's why we are trying our best to prepare for the exam．（ ）
A．untilB．whenC．unlessD．how
Neither Saturday nor Sunday________ OK because I will be quite busy these two days.
| A． |
are |
B． |
is |
C． |
am |
D． |
be |
The Forbidden City (紫禁城), the largest palace in the world, ________ more than 600 years ago.
| A． |
built |
B． |
were built |
C． |
was built up |
D． |
was building |
Students ________ play with fire in the classroom. It’s quite dangerous.
| A． |
mustn’t |
B． |
must |
C． |
couldn’t |
D． |
could |
I began to teach ________ English when I was twenty-two years old.
| A． |
they |
B． |
their |
C． |
theirs |
D． |
them |
Would you like to go to the open-air concert at school? It’ll start in ________ hour and ________ half.
| A． |
an; an |
B． |
a; an |
C． |
an; a |
D． |
a; a |