下列表示物质结构的化学用语或模型图正确的是[ ]
A.HClO的结构式:H-Cl-O
B.14C的原子结构示意图:
C.聚氯乙烯的结构简式:
D.丙烷分子的球棍模型示意图:
答案:D
________, it began to rain unexpectedly.
A.While cleaning the machine
B.To clean the machine
C.He was cleaning the machine
D.While he was cleaning the machine
石蜡热效应属()高频电流热效应属()
A.传导热
B.内热源性热
C.两者均是
D.两者均不是