Final answer:
Both sentences a and b demonstrate correct parallel structure, as they use consistent grammatical construction in the series of activities that Sasha's smartphone apps perform. Thus, the correct answer is c) Both (a) and (b).
Step-by-step explanation:
The question asks to identify which sentences demonstrate correct parallel structure. Parallel structure, also known as parallelism, occurs when components in a sentence are grammatically the same, or similar and this is important for clarity and can add balance to a sentence.
The correct answer to the question is option (a) as this sentence provides an example of parallelism as it uses a series of infinitive phrases ('to track,' 'monitor,' and 'schedule') that consistently describe the functions of the apps on Sasha's smartphone.
Option (b) also demonstrates parallel structure, even though it separates each function with 'to,' making it slightly more repetitive, yet still correct in terms of parallel structure. Therefore, the correct answer is (c) Both (a) and (b).