煤气管道在投运前必须进行强度试验。
参考答案:错
When asked to explain _____ he does to make his students so fascinated with his lessons, the teacher
paused and thought deeply. [ ]
A. what it is that
B. that what it is
C. what is it that
D. that what is it
请根据下图回答问题。
(1)若图中B是毛细血管,则根据血流方向,可判断图中A是____血管,C是_____血管。
(2)若图中B是手部毛细血管,则A内流的是____血,C内流的是____血,B处发生的是____交换。
(3)若图中B是肺部毛细血管,则A内流的是____血,C内流的是____血,B处发生的是____交换。