56. I found _______impossible for _______to work out the maths problem.
| A．it; him | B．it; he | C．that; him | D．that; he |
He slipped(溜进) into the classroom without ___________.
| A．noticed | B．noticing |
| C．being noticed | D．was noticed |
This special strain of rice makes _________ possible to produce one third more of the crop in the same fields.
| A．it | B．them | C．which | D．that |
---Is that the small town you often talk about?
---Right, just the one ______________ you know I used to work for three years.
| A．that | B．which |
| C．where | D．what |
Although the first part of the book is easy， the rest ______.
| A．has proved difficult | B． are difficult |
| C．is supposed difficult | D．have been found difficult |
----Where are you now?
----Well, I have arrived at _______ is called “the West lake”.
| A．which | B．that | C．where | D．what |