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

a. The implementation (A) of policies must begin (B) from block level, with incentives and tax benefits (C) that could aid manufacturers in their discernible (D)shift to alternatives for plastic.
b. The global (E) start-up landscape (F) is still dominated (G) by the West, though a gradual (H) shift  is underway.