Unfortunately, ____ stone hit him on ______ head and he got injured．

—What do you think of his opinion?—Nobody has given me _____ piece of advice.

We can never expect ________ bluer sky unless we create ________ less polluted world.

With ________ look of disappointment, he left the Student Union office. Without ________ knowledge of photographing, he missed the chance to be an editor of Babel.

Although their new factory building is still under          construction, we have already placed        order for 200 pairs of shoes.