A．suspiciousB．doubtfulC．dubiousD．unquestionableIt is __……

单项选择题It is well known that knowledge is the ______ condition for expansion of mind.

单项选择题Travelers in space have to ______ many discomforts in their spaceships.

单项选择题Congress was hit with a ______ mail campaign, and nearly 150 bills were introduced which would amend the Constitution to permit Bible reading and prayer in public places.

单项选择题The production of synthetics intensified the drain on energy resources, already sorely pressed by the increase in ______ demand.

单项选择题Moving down the hills and around the curves, the ______ of cars was not able to proceed faster than twenty miles an hour.

单项选择题Smoking should be banned in public places and great efforts should be made to inform young people of the ______ consequences of taking up the habit.

单项选择题Which of the following is TRUE according to the passage

单项选择题The reason that the exceptional children receive so much concern in education is that ______.

单项选择题From its passage we learn that the educational concern for exceptional children ______.

单项选择题In Paragraph 2, the author cites the example of the leading actor on the stage to show that ___.