correctness of a sentence [closed]

A sentence from an option of a multiple-choice question in ACT English:

Eventually, snails evolved that would use mucus to build small rafts of air bubbles on which they could float to the surface of the ocean to feed.

Is this a grammatically correct sentence? I feel like there are two predicates: evolved and would use.

Solution 1:

Eventually, snails evolved that would use mucus to build small rafts of air bubbles on which they could float to the surface of the ocean to feed.emphasized text

It's fine. There are indeed two predicates because there are two clauses: a matrix (main) clause (the sentence as a whole) and a subordinate relative clause ("that would use mucus to build small rafts of air bubbles on which they could float to the surface of the ocean to feed") modifying "snails".

The relative clause is postposed over the verb "evolved", but there is no grammatical error or ambiguity about its antecedent.

Solution 2:

A shortened and grammatically uncontroversial form of such a sentence might be Eventually, snails that use mucus evolved.

To put your original sentence into this form with a terminal evolved requires the reader to wait a long time for the main verb evolved, as in some long German sentences. We are not accustomed to such long waits in English, so it seems reasonable to use your original form instead, regardless of any other consideration.