he started the engine, released the hand break, and checked the mirror.\n\nparallel\nnot parallel

Brief Explanations:

Parallelism in grammar requires that items in a series or list follow the same grammatical structure. In the sentence "He started the engine, released the hand break, and checked the mirror," all three actions are expressed using the same pattern: a past-tense verb followed by a direct object (started the engine, released the hand break, checked the mirror). Because the grammatical form is consistent across all elements of the list, the sentence demonstrates correct parallel structure.

Answer:

Parallel