It was 2 months _____the young man mastered the skill of running the machine introduced from Korea.1since 2 before2对翻译

问题描述:

It was 2 months _____the young man mastered the skill of running the machine introduced from Korea.
1since 2 before
2对
翻译

应该before.
since与完成时对应,如果用since,应该it has been 2 months

since
因为since后面加过去时间点

选2,before.因为第一按照语境句子所表达的意思,只能选before.它的意思是:两个月以前,这个年轻人掌握了一门从韩国引进的机器的操作技能.第二,since一般都要和完成时态连用,后面跟一个时间状语从句.

翻译:年轻人花了2个月掌握了从韩国引进的机器的操作技能。
是选2.before。 选1的话就是用完成时态,而不是was