the rules of gift giving in USA vary a lot,and___them can result in great embrassmentA.don't know B.not knowing选哪个,并且说一下为什么
问题描述：
the rules of gift giving in USA vary a lot,and___them can result in great embrassment
A.don't know B.not knowing
选哪个,并且说一下为什么
答
选B 这里是现在分词短语作主语 不是主语分句 而且是现在分词短语的否定
答
B...
主语从句...
not knowing them
+
can result
+
in great emabrassment