The Internet celebrated its birthday on September 2nd, by which time 40 years _______ since the first successful transfer of data between two puters
A.has passed
B.had passed
C.passed
D.have passed
网友回答
B解析考查时态，by which time引导定语从句，by+过去时间，谓语用过去完成时，句意是：互联网在九月二日庆祝了自己的生日，到这个时间时间为止自从两台计算机之间的第一个成功的通过的数据传输已经过去有40年了。选B。