We can learn from Paragraph 4 that______.
A. ships without crew will soon replace traditional ones
B. most air crashes are caused by operational mistakes
C. erewless ships are favoured just because of safety
D. human hands are more reliable than computers
查看答案
【C19】
A. which
B. there
C. where
D. that
Ships with crew are more costly mainly because of______.
A. pay and accommodation for sailors
B. hotel facilities needed on board
C. expenditure on more fuels
D. heating and plumbing
斯金纳认为学习的实质就是“反应概率上的一种变化”，这种变化可用操作性条件反射来解释。()
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