骨质疏松症以腰背痛最为明显,为( )疼痛,活动时加重,休息后减轻。
A.间断性
B.持续性
C.偶然性
D.一阵性
参考答案:B
This is the first time that we ________a film in the cinema together as a family .
A.see
B.had seen
C.saw
D.have seen
单轨吊驱动轮的直径不得小于()mm,否则必须更换。