CableTVbeganin1948intheUSA,butittook50years

问题详情：

 Cable TV began in 1948 in the USA, but it took 50 years ________ 66 percent of American households had it.

A. before                        B. when                        C. after                         D. until

【回答】

A

知识点：连词

题型：选择题