Question

which sentence or sentences have correct parallel structure?
both short-term and long-term comets orbit around the sun, but as their name implies, short-term comets take less time to complete their orbits.
both short-term comets and long-term comets orbit around the sun, but as their name implies, short-term comets take less time to complete their orbits.

Explanation:

Parallel structure requires balanced grammatical forms for paired items. The first sentence uses the parallel structure "Both short-term and long-term comets" (adjective phrases modifying the noun "comets" uniformly). The second sentence uses "Both short-term comets and long-term comets", which also maintains parallelism by pairing two identical noun phrases. Both sentences have correct parallel structure as their paired elements follow the same grammatical pattern.

Answer:

1. Both short-term and long-term comets orbit around the sun, but as their name implies, short-term comets take less time to complete their orbits.
2. Both short-term comets and long-term comets orbit around the sun, but as their name implies, short-term comets take less time to complete their orbits.