Solution

(b)the end of the effect of tip preference

If the bushes are cut too close to the bud, the wood above the bud usually dies, resulting in dead tips on the ends of the branches. When a pruning cut is made, the nearest bud or buds normally form a new growing point. When a terminal is pruned out, the closest side buds grow considerably faster than they would otherwise, and the bud closest to the pruning cut becomes the new terminal.