Answer:
d. usually require longer-term planning than other market mix elements because channel decisions are more difficult to change quickly.
Step-by-step explanation:
IF you decide to use your own truck to move your product, you can't go back from that after 2 weeks, you invest time picking which truck to buy, time hiring drivers, time chequing routes, now you can just go back and make a third party do it because, you are running a lot of costs.
The channel of distribution must be set as a long-term strategy that will yield benefit through time.