In Imperfectly Competitive Markets,"administered" Prices Usually Change Than Prices in Perfectly

In imperfectly competitive markets,"administered" prices usually change than prices in perfectly competitive markets,because _ .

A) less often; changing prices is costly
B) more often; perfectly competitive firms are price takers
C) more often; price becomes a strategic choice
D) more often; they are more flexible
E) less often; changing prices is costless