The U.S. has to deal with the problems arising from vehicle use because______.
A.most Americans are reluctant to switch to public transportation systems
B.the present level of oil prices is considered unacceptable
C.other countries will protest its increasing greenhouse emissions
D.it should take a lead in conserving natural resources
第4题
配戴渐变焦镜片看远,配戴者被迫仰起头,证实()。
A.远用球镜过负欠正
B.远用球镜过正欠负
C.远用柱镜轴位或焦度有误
D.远瞳距有误
第6题
配戴渐变焦镜片看近,用眼疲劳,须将目标移远,证实()。
A.近附加光度欠正过负
B.双近附加光度不平衡
C.近附加光度过正欠负
D.近光心距有误
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