门式钢管脚手架的门架之间必须满设交叉支撑。当架高≤45m时,水平架应至少()步设一道。
A.、一
B、两
C.、三
D.、四
参考答案:B
Tourist excitement has built up _______ new places of interest were opened two years ago.
[ ]
A. as
B. since
C. only if
D. even though
感染艾滋病毒的孕妇在怀孕期可能会导致胎儿的感染,请问这种传播病原体的方式应称为()
A.血源性传播
B.医源性传播
C.水平传播
D.空气传播
E.垂直传播