平面四杆机构有无急回特性取决于极位夹角是否大于零。 ()
Which of the following is INCORRECT？
A. The U.S. has wide plains of lakes and rivers of different sizes.
B. The U.S. has thousands of lakes and rivers of different sizes.
C. The U.S. has hot deserts and cool forests.
D. The U.S. has a coastline several hundred miles long.
“五四运动”中的“德先生和赛先生”分别指的是“民主和科学”。()
Why does the man want to move out of the students dorm？
A. The apartment is cheaper than the dorm.
B. Smoking is forbidden in the dorm.
C. The dorm is too noisy for him to write his essays.
D. He can"t get along with his roommates.
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