SAT IP题提问In context,which of the following revisons would NO

SAT IP题提问
In context,which of the following revisons would NOT imrove sentence 9 (reproduced below)?
We know that she tried to learn about everything she found--I believe she would have much to say about the many countries she lived in.
A Delete " we know that"
B Delete "I believe"
C Change "found" to "encountered"
D Change the dash to a semicolon
E Change "much" to "tons of things"
正确答案选的E，但我觉得D也有错，换成逗号后不是成run-on 句型了么?