<p>Some plants use chemical signals (A)[that repel] insects, and (B)[also, these] signals help to put neighboring plants on alert (C)<a href="D">so they can</a><a href="E">mount their own defenses.</a>No error.</p>
<p>The answer is B. It sounds awkward to me too, but what is the EXACT error and HOW can I CORRECT it?</p>
<p>Is this a right correction: Some plants use chemical signals that reple insects, and these signals also help to put neighboring plants on alert so they can mount their own defenses...</p>
<p>:)</p>