More than one example ______ necessary to make the students understand this rule clearly.
A. should be
B. is
C. are
D. have been
In England, people put their ______ first.
A. given names
B. full names
C. family names
D. English names
The trouble with such resources as coal,oil and gas ______ that they are not renewable.
A. has been
B. are
C. have been
D. is
维生素C注射剂的正常情况下的颜色和性状是
A. 无色澄明液体
B. 红色浑浊液体
C. 棕色澄明液体
D. 黄色澄明液体
E. 无色浑浊液体