第28题: [单项选择]The purpose of this system is ______ trade flow as freely as possible, making sure that there are no undesirable side-effects. A. help B. to help C. helping D. in helping 参考答案:B 答案解析:[理由] 凡以表“目的”、“欲望”、“梦想”与“计划”等名词作主语时,应在be动词后接不定式短语作表语。 [例] Their plan is to change