El Nino, the periodic abnormal warming of the sea surface off Peru, a phenomenon in which changes in the ocean and atmosphere combine allowing the warm water that has accumulated in the western Pacific to flow back to the east.
(A)a phenomenon in which changes in the ocean and atmosphere combine allowing the warm water that has accumulated
(B)a phenomenon where changes in the ocean and atmosphere are combining to allow the warm water that is accumulating
(C)a phenomenon in which ocean and atmosphere changes combine and which allows the warm water that is accumulated
(D)is a phenomenon in which changes in the ocean and atmosphere combine to allow the warm water that has accumulated
(E)is a phenomenon where ocean and atmosphere changes are combining and allow the warm water accumulating
题目分析：必须加be动词啊，否则没有谓语了，答案在D和E里面。D和E一个用to allow一个用and allow，根据意思，allow无法和前面的combine形成语意的并列，选D。而且E中的那个are combing这个进行时态用于表达一个客观事实也不是很妥当，应该用D中的一般现在时比较合适！
