prep2-73 求助 和白勇的语法有冲突 关于during the last ice age

73.   (28441-!-item-!-188;#058&003975)

Radiocarbon dating of fossils taken from caves on islands along southeastern Alaska's coast suggest that at least a portion of the area was remaining ice-free during the last ice age.

(A) suggest that at least a portion of the area was remaining

(B) suggest at least a portion of the area remaining

(C) suggests that a least a portion of the area remained

(D) suggests at least a portion of the area that had remained

(E) suggests at least a portion of the area to have remained

按照语法排除应该是C，但是想到白勇语法提到during last ＋时间短语，则时态就是完成时，那么最终还是选了E，错了

答案是C

请大家指点一二

remain本来就可以表示一个持续的状态了 why bother to add had remained? it's like STAY/KEEP

suggest=显示...不是建议的意思...suggests that+ (fact)...

3X!