在1962年和1952年英国伦敦两次烟雾事件中发生多种急慢性疾病,其中起主层作用的污染物是( )。
A.SO2
B.烟尘
C.NOX
D.酸雾
E.甲醛
参考答案:B
小儿肌性斜颈的病变肌群是()
A.颈夹肌
B.颈阔肌
C.胸锁乳突肌
D.斜方肌
E.颈半棘肌
As a vessel sinks to a depth of 15 feet,the hydrostatic trip releases the liferaft container from its cradle by().
A.breaking the weak link
B.releasing the tie-down strap
C.pulling the operating cord
D.releasing the CO2 canister