China successfully hosted the Belt and Road Forum_________May，2017．（ ）
| A． |
on |
B． |
in |
C． |
by |
Don't forget ________ the windows before you leave．（ ）
A．to closeB．closingC．closed
Is our playground still over there？
No， a large library ________ on it two years ago．（ ）
A．is builtB．was builtC．has built
Slow down! Someone ________ the road．
Easy． I will．（ ）
A．has crossedB．was crossing
C．is crossing
Playing computer games too often ________ bad for us．（ ）
A．amB．isC．are
Stephen Hawking， a great scientist， died ________ the morning of March 14， 2018．（ ）
A．onB．inC．at