I would go with E.
A. Flouridation over a certain prescribed level has been shown to lead to a general weakening of teeth.
-> the maximum level has been set. so no need to worry about this.
B. There is no record of the long-term effects of drinking flouridated water.
-> 10 years of research should be sufficient...
C. The people to be affected by flouridation claim that they have not had sufficient opportunity to voice their views.
-> A kind of restatement of those who object (last sentence)
D. Flouridation is only one part of general dental health.
E. Water already contains natural flouride.
-> Answer. If water already contains flouride, then why need flouridation? The maximum, not the minimum level of flouride required for strengthening teeth exists.