单选题 People who live in the country probably do more driving than walking because _______.

单选题 Every four hundred copies of a forty-paper newspaper will need ______.

单选题 The Vienna survey may help to explain __________ .

单选题 Scandinavia began to make paper__________.

单选题 The purpose of the second paragraph is to list some __________ .

单选题 Where was paper invented?

单选题 All over the world, trees are being cut down___________than they are being planted.

单选题 To reach the third floor of a building, it would probably be most healthful ___________ .

单选题 A conclusion that can be drawn from this passage is that __________ .