问一道GMAT数学和CR

题目

问一道GMAT数学和CR
In order to withstand tidal currents,juvenile horseshoe crabs frequently burrow in the sand.Such burrowing discourages barnacles from clinging to their shells.When fully grown,however,the crabs can readily withstand tidal currents without burrowing,and thus they acquire substantial populations of barnacles.Surprisingly,in areas where tidal currents are very weak,juvenile horseshoe crabs are found not to have significant barnacle populations,even though they seldom burrow.Which of the following,if true,most helps to explain the surprising finding?
A.Tidal currents do not themselves dislodge barnacles from the shells of horseshoe crabs.
B.Barnacles most readily attach themselves to horseshoe crabs in areas where tidal currents are weakest.
C.The strength of the tidal currents in a given location varies widely over the course of a day.
D.A very large barnacle population can significantly decrease the ability of a horseshoe crab to find food.
E.Until th

答案

1.幼年crab怕被冲走,要burrow,所以壳上barnacles少成年crab不怕被冲走,不要burrow,所以壳上barnacles多问,为什么当幼年crab不要burrow的时候,壳上的barnacles还是少?答,在长成成年crab之前,他们的壳每年都要换（换言...