单选题
Siebes' invention was not a perfect one, because
A、
too great a supply of air could result in a sudden rise to the surface.
B、
a sudden dive into deep water could cause the crushing of the body.
C、
the air pipe attached to a machine could be above the surface.
D、
both A and B.
【正确答案】
D
【答案解析】
[解析]由第三段中的“But there were two dangers to...One was...The other was...”可知答案为D。故应选D。
提交答案
关闭