【C5】A．requireB．requestC．urgeD．appeal

【C16】A．to requireB．requiredC．requiringD．are required

【C5】A．timeB．requestC．meansD．obligation

【C17】A．RequireB．RequiringC．To RequireD．Required

【C7】A．answerB．requestC．questionD．difficulty

【C14】A．answerB．requestC．questionD．difficulty

【C3】A．requireB．receiveC．obtainD．achieve