Father brought his little boy to a concert．But he was too young to sit ___ the whole concert．（ ）
| A． |
for |
B． |
with |
C． |
during |
D． |
through |
If we are interested in something， our brain is_____and it is also easier for us to pay attention to it for a long time．（ ）
| A． |
active |
| B． |
more active |
| C． |
the most active |
Since 1990， Project Hope_____millions of students from poor families realize their dreams．（ ）
| A． |
will help |
B． |
has helped |
C． |
helps |
The BBC's documentary Du Fu： China's Greatest Poet explains_____Du's works have been popular for centuries．（ ）
| A． |
when |
B． |
whether |
C． |
why |
With the help of Air Classroom， students_____ keep learning even with schools closed．（ ）
| A． |
can |
B． |
must |
C． |
should |
Drugs are harmful to people's physical and mental health． We teenagers must_____them．（ ）
| A． |
take care of |
| B． |
keep away from |
| C． |
get used to |