sat平行结构的问题mostenduranceathletesfindthatregulartrainingisessential(toimprove)racetimes,butathletictalentalsoplaysabigroleindetermininghosfastanathletewillbeonraceday.Whatiswrongwiththephrasebracketed?

Question

sat 平行结构的问题
most endurance athletes find that regular training is essential (to improve) race times,but athletic talent also plays a big role in determining hos fast an athlete will be on race day.
What is wrong with the phrase bracketed?Does it have anything to do with parallel structure?

Answer 1

both...and...用于连接两个结构平行的成份.
但也偶有例外,以下句子中就有 “both 不定式 and 动词”：
The following brief notes are indications as to how one might use drama both to stimulate and support work in specific curriculum areas.
The approach was collaborative:teachers were invited to work with the team as equal partners in the attempts both to investigate and find solutions to the GIST problem.
The critics argued that some cut-back or restraint in spending or provision was necessary,both to fund tax cuts and allow for the concentration of resources on the most needy.
（3例均来自British National Corpus）