[多选题]三角皮带是三角带中用得最多的一种，它是由（ ）和包布层制成的无端环形胶带。
A.A.强力层
B.B.伸张层
C.C.压缩层
D.D.摩擦层

（2020年真题）下列关于地方政府债券的说法，错误的有（　　）

Ⅰ地方政府债券是地方政府根据本地区经济发展和资金需求状况，以承担还本付息责任为前提，向社会筹集资金的债务凭证

Ⅱ地方政府债券是地方政府根据本地区经济发展和资金需求状况，以承担偿还本金责任为前提，向社会筹集资金的债务凭证

Ⅲ地方政府债券是地方政府根据本地区经济发展和资金需求状况，以承担还本付息责任为前提，向社会筹集资金的权益凭证

Ⅳ地方政府债券是地方政府根据本地区经济发展和资金需求状况，以承担偿还利息责任为前提，向社会筹集资金的债务凭证

If there is no difference in general intelligence between boys and girls, what can explain girls’ lack of success in science and mathematics
It seems to be that their treatment at school is a direct cause. Mathematics and science are seen as mainly male subjects, and therefore, as girls become teenagers, they are less likely to take them up. Interestingly, both boys and girls tend to regard the "male" subjects as more difficult. Yet it has been suggested that girls avoid mathematics courses, not because they are difficult, but for social reasons. Girls do not want to be in open competition with boys, nor do they want to do better than boys because they are afraid to appear less ladylike and attractive.
However, if we examine the performance of boys and girls who have undertaken mathematics courses, there are still more high-achieving boys than there are girls. This difference appears to be worldwide. Biological explanations have been offere
A. Why do teenage girls avoid mathematics courses
B. They think mathematics is not interesting.
C. They think mathematics is difficult.
D. They think mathematics is competitive.
E. They think boys will not like it either.