[单选题]接头螺栓折断、变形，严重锈蚀、丝扣损坏或杆径磨耗超过（）mm不能保持规定的扭矩。
A.2
B.3
C.4
D.5

Humans are forever forgetting that they can’t control nature. Exactly 20 years ago, a Time magazine cover story announced that “scientists are on the verge of being able to predict the time , place and even the size of earthquakes.” The people of quake-ravaged Kobe (神户)learned last week how wrong that assertion was.
None of the methods conceived two decades ago has yet to discover a uniform warning signal that preceded all quakes, let alone any sign that would tell whether the coming temblor (震动) is mild or a killer. Earthquake formation can be triggered by many factors, says Hiroo Kanamori, formation can be triggered by many factors, says Hiroo Kanamori, a seismologist (地震学家)at the California Institute of Technology, So, finding one all - purpose warning sign is impossible. One reason: Quakes start deep in the earth, so scientists can’t study them directly . If a quake precursor were found, it would still be impossible to warn humans in advance of
A. 1, it can be inferred that.A. scientists can never be able to predict the coming of earthquakes.
B. the existing power on predicting earthquakes is somewhat exaggerated.
C. quite a lot of scientific assertions are groundless.
D. earthquake predictions are beyond the reach of scientists.