43.What is the fundamental idea that the author keeps in mind in unclogging the drain?
(A) Drain cleaners made of toxic chemicals are inevitable.
(B) People should avoid chemical cleaners as much as possible.
(C) It seems out of the question to do drain clogging without man-made fluids.
(D) A small room is good enough for a technician to deal with drain clogging since they do not
have any ventilation trouble.

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