In order to withstand tidal currents,juvenile horseshoe crabs frequently burrow in the sand.Such burrowing discourages barnacles from clining to their shells.When fully grown,however,the crabs can readily withstand tidal currents without burrowing,and thus they acquire substantial populations f barnacles.Surprisingly,in areas where tidal currents are very weak,juvenle hreshoe 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 disloge barnacles from the shells of horseshoe crabs.
E.Until they are fully grown,horseshoe crabs shed their shells and grow new ones several times a year.
不理解A为什么错，E为什么对。求NN解释作者: rudder86 时间: 2011-1-11 20:55
