1.The passage is mainly about _____.

1.The passage is mainly about _____.
A.the defects of electronic devices
B.a possible cause of aircraft crashes
C.a new regulation for all airlines
D.effective safety measures for air flight
2.What is said about the over 100 aircraft incidents in the past 15 years?
A.They were suspected to have resulted from electromagnetic interference.
B.They may have been caused by the damage to the radio systems.
C.They may have taken place during take-off and landing.
D.They were proved to have been caused by the passengers' portable computers.
3.Few airlines want to impose a total ban on their passengers using electronic devices because _____
A.they don't believe there is such a danger as radio interference
B.the harmful effect of electromagnetic interference is yet to be proved
C.they have other effective safety measures to fall back on
D.most passengers refuse to take a plane which bans the use of radio and cassette players
4.Why is it difficult to predict the possible effects of electromagnetic fields on an airplane's computers?
A.Because it remains a mystery what wavelengths are liable to be interfered with.
B.Because experts lack adequate equipment to do such research.
C.Because it is extremely dangerous to conduct such research on an airplane.
D.Because research scientists have not been able to produce the same effects in labs.
5.It can be inferred from the passage that the author _____.
A.is in favor of prohibiting passengers' use of electronic devices completely
B.regards it as unreasonable to exercise a total ban during flight
C.hasn't formed his own opinion on this problem
D.has overestimated the danger of electromagnetic interference