问题
选择题
_______cloning human embryos is not legal in many countries, some scientists are already pushing ahead with research in order to produce a cloned human baby.
A．While
B．When
C．Since
D．if only
答案
A
题目分析：考查连词：A. While虽然,B. When当…时候，C. Since既然D. if only 但愿，句意：虽然克隆人类胚胎是违法的，但一些科学家已经在努力推进研究为了制造克隆的人类婴儿。选A。
点评：考查连词主要是弄清每个冠词本身的含义，做题时一定要根据上下文的逻辑关系选择。