A．A球受的浮力大
B．B球受的浮力大
C．两球所受浮力一样大
D．无法判断
答案：A
Teachers always expect their students to realize that hard work ________. [ ]
A. puts off
B. gives off
C. pays off
D. sees off
下列腺体的唾液中硝酸盐最高的是（）
A.磨牙后腺
B.唇腺
C.下颌下腺
D.腮腺
E.舌下腺
