托业考试

根据网考网考试中心的统计分析，以下试题在2018/7/26日托业考试习题练习中，答错率较高，为：90%
【单选题】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