Question

【题目】The scientists will succeed in their experiment______ they give up.

A. unless B. if C. after D. until

Answer 1

【答案】A

【解析】

试题分析：句意：除非科学家们放弃，否则他们将会实验成功。 unless 连词，除非，引导条件状语从句。所以选A。