Mr． Black walked around and offered help____we were doing an experiment．（ ）
| A． |
while |
B． |
although |
C． |
until |
D． |
unless. |
There is a______in my neighborhood and I often go there to see tigers．（ ）
| A． |
zoo |
B． |
bank |
C． |
school |
This is the best book I have ever read．I like it very much．（ ）
| A． |
which |
B． |
that |
C． |
who |
D． |
when |
It's nice to see you again．We each other since 2016．（ ）
| A． |
won't see |
B． |
haven't seen |
| C． |
don't see |
D． |
didn't see |
There some students on the playground．（ ）
| A． |
is |
B． |
have |
C． |
has |
D． |
are |
have you felt like this？
Three days．（ ）
| A． |
How long |
B． |
How often |
C． |
How much |
D． |
How many |