（），we would have finished it then.

A:If had we had better equipment B:Had we had better equipment C:Had had we better equipment D:We had had better equipment

What we have seen is ______.

A:from what we heard B:all what we heard C:to what we have heard D:from what we have heard

I think this is the first time that we have met．（） anywhere．

A:Before have we never seen each other B:Never before we have seen each other C:Each other have We seen never before D:Never before have we seen each other

Economics, several courses of which I have taken thus far, ______ to be difficult but useful for almost all students. ( )

A:prove B:proves C:have been proved D:are proved

Economies, several courses of which I have taken thus far, ______ to be difficult but useful for almost all students.

A:prove B:proves C:have been proved D:are proved

_____about it earlier, we could have wamed people of the danger.

A:Would we know B:Should we know C:Have we known D:Had we known

We find it hard to break free from ideas connected with living on the earth because

A:it demands too great an effort for us to do so. B:we are too familiar with the way things are to question the ideas. C:we have proved that those ideas are correct. D:we are so sure of ourselves that we never doubt anything on the earth.

We find it hard to break free from ideas connected with living on the earth because

A:it demands too great an effort for us to do so. B:we are too familiar with the way things are to question the ideas. C:we have proved that those ideas are correct. D:we are so sure of ourselves that we never doubt anything on the earth.