1 The conclusion of the passage is that, because of safety concerns, more research and testing ought to be done before microwaves become standard household appliances. If, however, research and testing are ineffective means of discerning safety problems (as choice C says), then research and testing would be irrelevant. This criticism seriously weakens the conclusion. So choice C is the correct answer.

2 If many microwave ovens have been found to leak radioactive elements (as choice D says), then the conclusion that microwaves should not be standard appliances until they are more carefully researched and tested is further strengthened because more safety concerns need to be addressed. So, choice E is the correct answer.