两道LSAT逻辑题---请教

20. In North America there has been an explosion of public interest in, and enjoyment of , opera over the last three decades. The evidence o fthis explosion is that of the 70 or so professional opera companies currently active in North America, 45 were founded over the course of the last 30 years.
The reasoning above assumes which one of the following?
B there were fewer than 45 professional opera companies that had been active 30 years ago and that ceased operations during the last 30 years.
E The 45 most recently founded opera companies were all established as a result of enthusiasm on the part of a potential audience.

B. Why E is not right?

21. Although many seventeenth-century broadsides, popular ballads printed on a single sheet of paper and widely sold by street peddlers, were moralizing in nature, this is not evidence that most seventeenth-century people were serious about moral values. While over half of surviving broadsides contain moralizing statements, and it is known that many people purchased such compositions, it is not known why people purchased such compositions, it is not known why they did so, nor is known how their own beliefs related to what they read.
Which one of the following, if true, most strengthens the argument?
B In many moralizing ballads, the moral content was confined to a single stanza expressing a pious sentiment tacked onto a sensaionalized account fo crime and adultery.
E Well-educated people of the seventeenth-century held broadsides in contempt and considered broadside peddlers to be disreputable vagrants.

B. I choosed E. Why B is right?