It's a risky proposition going outside of what's printed and changing the answers to be "also correct."
In this case, you're right that A goes out of scope by mentioning the other types of cancers. However, it also doesn't address the implied causality in the argument. The author seems to conclude that consuming sugar CAUSES cancer. However, the evidence simply says that those people who are more likely to consume sugar are also more likely to have this specific kind of cancer. Fixing the type of cancer in A doesn't completely fix the argument, but it plugs the biggest hole.
D. Doesn't weaken the argument - just addresses another characteristic of these people. In fact, this characteristic might, given the right evidence added to it, strengthen the argument...
E. Again - we have to go back to "sugar causes cancer" as the bad logic here. The evidence is "tendency to consume sugar correlates to tendency to contract this specific cancer." E doesn't weaken this.