Directions: In the sentence, certain words are in bold and numbered from A to H, which are the possible pairs to be interchanged. Choose the pair(s) of the words that need(s) to be interchanged to make the sentence grammatically correct and meaningful.

a. The weather presented(A) a particular challenge, especially(B) for American servicemen specify(C) to subarctic conditions(D)
b. Instead of persuading(E) the user to unaccustomed(F) requirements, the analyst will be driven(G) by the user to meet key needs(H).