The philanthropist devoted himself _______the poor.
Answer Details
The correct option is "to helping."
The phrase "devoted himself" implies that the philanthropist committed himself to a particular action or cause. In this case, the action is helping the poor.
The preposition "to" is commonly used after "devoted" to indicate the thing or activity that someone is dedicated to. Therefore, "devoted himself to helping the poor" means that the philanthropist committed himself to the activity of helping the poor.
Options A and D ("by helping" and "in helping") could also make sense grammatically, but they do not convey the same sense of dedication and commitment as "to helping." Option B ("to be helping") is incorrect because it uses the infinitive form "to be" instead of the gerund form "helping," which is necessary after "devoted."