_______,but it is also a great way to lower the number of greenhouse gases in the air.
| A．Not only a fun thing is it to do | B．Not only a fun thing to do it is |
| C．Not only it is a fun thing to do | D．Not only is it a fun thing to do |
Why ____ you keep troubling your mother with such question while he is busy .
| A．can | B．will | C．would | D．must |
I''m surprised that he ____ to help me when I needed his help .
| A．should refuse | B．would have refused |
| C．should have refused | D．may have refused |
The men got out and pushed the bus . But it ____ move , not one bit .
| A．couldn''t | B．wouldn''t | C．needn''t | D．shouldn''t |
The fire spread through the hotel very quickly but everyone ____ get out .
| A．had to | B．would | C．could | D．was able to |
It''s nearly seven o''clock . Jack ____ be here at any moment .
| A．must | B．need | C．should | D．can |