In the following question, the given sentence has four parts marked P, Q, R, and S. Choose the part of the sentence with the error and mark as your answer. If there is no error, mark 'No error (S)' as your answer.
Throughout history, (P)/ humans has existed side-by-side (Q)/ with bacteria and viruses. (R)/ No error (S)

Correct option is B

Option (b) contains an error.
Error Identification: The verb "has" is incorrect for the plural subject "humans." It should be "have."
Grammatical Explanation: The subject "humans" is plural, so it requires the plural auxiliary verb "have."
Corrected sentence: "Throughout history, humans have existed side-by-side with bacteria and viruses."
Explanation: The plural subject "humans" must agree with the plural verb "have."