The doctor looks tired and sleepy ________ he stayed up late to look after his patients yesterday．（ ）
| A． |
because |
B． |
if |
C． |
unless |
I'm going to choose some online courses with a friend of ________ to improve our English．（ ）
| A． |
me |
B． |
my |
C． |
mine |
"Excuse me， could you tell me where I can buy a guidebook？"
"Sorry， I'm new here． You ________ ask the policeman over there．"（ ）
| A． |
shall |
B． |
can |
C． |
must |
"Meatout Day" is ________ March 20th． Many people in the world don't eat any meat that day．（ ）
| A． |
at |
B． |
in |
C． |
on |
" ________ fast Guizhou Province is developing!"
"Yes． It hosts the Big Data Expo every year．"（ ）
| A． |
What |
B． |
How |
C． |
What a |