The most appropriate answer to complete the sentence is Option A.
In the first paragraph itself, there is a mention about Mr. Abid Surti going door to door along with a plumber and an assistant. The passage clearly states the willingness of people when the services offered are free, and that too something of least importance according to them. Another reason is the fact that certain lower class families cannot afford to pay for a plumber, and here they get a chance to hire one for free.
Thus, as mentioned in Option A, people are willing to accept services by Mr. Surti, in the assistance of a plumber.
The other options B, C and D, are not the reasons why people are more willing to accept Surit's services (at least we do not have the evidence to prove that in the passage) hence eliminating them as answers.