Final answer:
Option d has the correct parallel structure because it maintains a consistent past tense verb form for all actions: 'The fish jumped out of the cool mountain stream, plunged back into the water, and swam against the current.' Option D is the correct answer.
Step-by-step explanation:
The question posed concerns the concept of parallel structure in sentence construction. Parallel structure, also known as parallelism, is the use of components in a sentence that are grammatically the same or similar in their construction, sound, meaning, or meter. This enhances the readability and flow of a sentence and ensures that ideas are presented with a balanced rhythm and style.
Looking at the given options, the requirement is for elements that describe the actions of the fish to follow a similar grammatical structure. The first option lacks parallelism because it mixes verb forms ('jumped', 'back into' and 'swimming'). The second and third options also disrupt parallelism - one through inconsistent verb tense ('jumped', 'plunges', 'swims') and the other through incorrect use of will ('it plunged', 'and will swam').
Option d is the sentence with a correct parallel structure: 'The fish jumped out of the cool mountain stream, plunged back into the water, and swam against the current.' Each verb ('jumped', 'plunged', and 'swam') is in the past tense, maintaining a consistent grammatical structure throughout the sequence of actions.