The reason ________ he referred to for his success is ________ he always working hard.

A) why, that B) why, because C) that, that D) that, because

The teachers hope the little ________ has been learned will be useful when they leave school.

A) that B) what C) knowledge D) which

“This is a window, ________ the sun comes in.” said the lady to her baby.

A) where B) which C) by which D) through which

 Living in the western part of the country has its problems, ________ obtaining fresh water is not the least.

A) with which B) for which C) of which D) which

These students will graduate from the university next summer, ________ they will have studied here for four years.

A) by then B) by that time C) by the time D) by which time

 Many new means of transportation have been developed in our century, ________ perhaps the hovercraft.

A) and the strangest of which is B) the strangest of which being

C) the strangest of which is D) and the strangest of them being

In 1997, the take-home food sold by supermarkets made up 21 per cent of the total, while _____supplied by fast restaurants was 48 per cent.

A) that B) which C) it D) one

He made another wonderful discovery, ________ of great importance to science.

A) which I think is B) which I think it is C) which I think it D) I think which is