Both Writewell and Express provide round-t

问题：

Both Writewell and Express provide round-the-clock telephone assistance to any customer who uses their word-processing software. Since customers only call the hot lines when they find the software difficult to use, and the Writewell hot line receives four times as many calls as the Express hot line, Writewell’s word-processing software must be more difficult to use than Express’s.
Which of the following, if true, most strengthens the argument above

A．Calls to the Express hot line are almost twice as long, on average, as are calls to the Writewell hot line.

B．Express had three times the number of word-processing software customers that Writewell has.

C．Express receives twice as many letters of complaint about its word-processing software as Writewell receives about its word-processing software.

D．The number of calls received by each of the two hot lines has been gradually increasing.

E．(E) The Writewell hot-line number is more widely publicized than the Express hot-line number.