Answer:
B. to prove that smartphone sensors are not for the user’s benefit
Explanation:
I believe the question is related to the article entitled "Smartphones put your privacy at risk."
The article tells people, especially the smartphone-users, about "invasive" apps and how they use the smartphone's sensor in order to steal information without the knowledge of the user. It provides evidence how the sensors are actually keeping track of the person's normal daily routine, which he is not aware of. It can then give others the information on where he lives or works.
The article doesn't discourage the readers from using smartphones, it simply tells information so readers will become aware. Using the smartphone is a trade-off, it doesn't involve balance between convenience and its risk.
So, this explains the answer.
