【C7】A．variationsB．consequencesC．effectsD．causes

【C7】A．atB．toC．forD．over

【C7】A．ensureB．approveC．supplyD．deliver

【C7】A．advantagesB．consequencesC．problemsD．potentials

【C7】A．resultB．reasonC．causeD．phenomenon

【C17】A．variationsB．vacanciesC．vibrationsD．ventilations

【C7】A．remainB．keepC．makeD．cause