If it ________ rained yesterday, Mary might have come.

1.   ?    not had
2.   ?    had not
3.   ?    wouldn't have
4.   ?    would not

The survey shows that the product will be popular in the market, ______ the company cuts down the selling price for 10%.

1.   ?    if
2.   ?    unless
3.   ?    when
4.   ?    whether

If I ______ seen it, I wouldn't have believed it possible.

1.   ?    had not
2.   ?    did not
3.   ?    wouldn't have
4.   ?    would not

You can’t rent any vehicle _______ you have license.

1.   ?    if
2.   ?    unless
3.   ?    that
4.   ?    when

If they _______ like it, they can have another one.

1.   ?    do not
2.   ?    didn't
3.   ?    will
4.   ?    won't

If the National Park __________constructed 30 years ago, the citizens might still be looking for recreation among the rocks.

1.   ?    had been
2.   ?    had not been
3.   ?    was
4.   ?    was not

We'll go on with the work, ________ we can find the essential tools or not.

1.   ?    unless
2.   ?     if
3.   ?    whether
4.   ?    no matter