A．problemB．causeC．resultD．resource

A．produceB．leadC．resultD．act

【C20】A．factB．caseC．resultD．contrast

【C18】A．finishB．closeC．resultD．end

【C14】A．challengeB．taskC．resultD．mistake

Despite scholars’ study, the （) of human beings is still unclear.A、originB、causeC、begin

【C9】A．WhatB．CauseC．ReasonD．Because