For a substantial price, several high-technology companies w

Using tech, one can know the risk to illnesses such as diabetes or heart disease.
But having a high-risk for a particular disease is no guarantee that one will acquire it
One can reduce the chances of falling prey to these illnesses through lifestyle choices anyway.

Conclusion: So finding out the amount of risk to illnesses is useless.

We need to weaken the argument. We need to say that finding out the risk to illnesses can be beneficial in some way. It can help us.

A) The author has assumed without reason that people are uncomfortable paying private companies for medical information that is so personal

The author has not assumed anything about whether people will want to pay or not for the tech. He just says why using the tech is irrelevant.

B)The author has underestimated the dangers associated with genetically determined diseases.

Not true. The author is not saying that the diseases are mild and should be ignored.

C) Knowing that one is at risk for a certain illness allows one the opportunity to modify one’s lifestyle accordingly.

Correct. This is a weakness of author's argument. He says knowing the risk is useless. But if knowing the risks can help people alter their lifestyle and take preemptive measures, that could be a reason in favour of finding out the amount of risk to illnesses.

D) The author assumes that people who are at risk for certain illness will take steps to reduce the risk.

This is not a weakness of his argument. The author does not assume anything about what people will do if they find out their risk. He says that using tech to find your risk is useless.

E) The cost of the DNA analysis is assumed to be too high for the vast majority of the population

No such assumption is made. Cost, whether high or low, is irrelevant. The author only talks about whether using tech is useful.

Answer (C)