41.
Your Answer is
Correct Answer is B
Explanation
The underlined part is the subject and predicate of the sentence, and the subject of To keep riders' clothing clean and dry should be bikes, so choose option B. The underlined part is the subject and predicate of the sentence, and the subject of To keep riders' clothing clean and dry should be bikes, so choose option B.
A item: they refer to unknown, because there are many plural nouns in the previous sentence.