She went to the bookstore and bought _________.
| A．dozen books | B．dozens books |
C．dozen of books | D．dozens of books |
Mathematics ____the language of science.
| A．are | B．are going to be | C．is | D．is to be |
Half of his goods ____ stolen the other day.
| A．are | B．were | C．is | D．was |
That they were wrong in these matters _____ now clear to us all.
| A．is | B．was | C．are | D．were |
Although the first part of the book is easy， the rest ______.
| A．are difficult | B．has proved difficult |
| C．is supposed difficult | D．have been found difficult |
When and where to build the new factory ____yet.
| A．is not decided | B．are not decided |
| C．has not decided | D．have not decided |