1. The airline industry is cutting its lowest discount fares more widely, more substantially, and earlier this year than it normally does at the end of the summer, a time during which travel usually decreases and the industry uses some lower fares for the attraction of passengers.

(A) during which travel usually decreases and the industry uses some lower fares for the attraction of

(B) during which travel usually decreases and therefore the industry will use some lower fares for the attraction of

(C) in which travel usually decreases and in which the industry therefore uses some lower fares attracting

(D) when travel usually decreases and the industry uses some lower fares to attract（D）

(E) when travel usually decreases and therefore the industry will use lower fares for the attraction of

答案没问题，想问下in which 和during which有什么区别吗？