答案：B

题目分析：考查固定句式。固定句式：祈使句+连词+陈述句=If条件句，主句。本句Bring the plants into a warm room, and they will grow quickly.="If" you bring the plants into a warm room, they will grow quickly. A项用于否定句中。故B正确。

点评：本题特别重要。固定句式：祈使句+连词+陈述句=If条件句，主句。还可以进一步转换成名词短语，+连词+陈述句的形式。