Question

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 at 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.

Answer 1

The correct option is C suggests that at least a portion of the area remained

The subject is 'dating' so the verb has to be the plural 'suggests', which brings us to C, D and E.

The subjunctive mood states that 'suggest' should always be followed by 'that'. Hence C is the correct answer.