Explanation:

Correct  answer is (c). There is an error in part C of the sentence. We have to replace ‘after’ with ‘with’ Regard someone or something with something (Idiom): to look upon someone or something with a certain attitude or with certain expectations.  Ex. The child regarded the teacher with a questioning expression.  The correct sentence would therefore be, "Water from shallow wells should be regarded with suspicion, as it may be contaminated."  Option C is hence the correct answer.