[SC悬赏令] 求解prep07-2-73，关于a least a ...

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
答案是C 我选的D 明白D 错在时态，但是C的a least a portion 我觉得有问题啊 读着很别扭，希望NN们帮忙解答~先谢啦！！！