Despite much research, there are still certain elements in the life cycle of the insect that ______ not fully understood.
A. are
B. were
C. is
D. was
查看答案
处方结构中的主要部分是
A. 处方前记
B. 医生签名
C. 处方编号
D. 处方后记
E. 处方正文
Writing stories and articles ______ what she enjoys most.
A. is
B. have been
C. was
D. were
In our country each boy and each girl ______ the right to receive a good education.
A. is
B. are
C. has
D. have
焊料熔化后润湿性的好坏与哪项条件无关
A. 被焊金属熔点
B. 被焊金属表面是否有氧化层
C. 被焊金属成分
D. 被焊金属表面粗糙度
E. 焊料的成分
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