The correct answers are B. The remaining leaves and the core of the lettuce plant are left intact and will continue to grow and produce more leaves and D. "Cut-and-come-again" is a repeated harvest technique in which only some of the leaves are harvested for a bit of fresh lettuce and for science samples.
Explanation:
One of the factors that make sentences correct is the agreement between subject and verb; in this way, it is expected a singular subject has a singular verb form and plural noun is followed by a plural verb.
This important grammatical rule is followed only in "the remaining leaves and the core of the lettuce plant are left..." because in this case both the subject and verb are plural, and in "Cut-and-come-again" is a repeated harvest technique..." because the subject "Cut-and-come-again" and the verb "is" are both singular. Therefore, only these two sentences are completely correct.
