Which is a key detail that supports the main idea that there are general principles that guide sports helmet design?
helmets must protect the face.
helmets must not prevent seeing or hearing.
scientists invent new plastics all the time.
materials used for police can be used in sports.

Helmets must not prevent seeing or hearing.

A general principle is almost like a rule. It is an agreed upon standard for a certain thing. In this case, the general principles or standards are for sports helmets. While it is a good idea in some sports for the helmet to protect the face, like the helmet of a hockey goalie, it is not necessary. In biking, horseback riding, baseball, and many other sports, face protection is not a necessity. However, helmets should not prevent seeing or hearing. They may reduce a person's field of vision or obstruct hearing slightly, but they should not prevent it completely. The other options about the type of plastics and materials are not guiding principles because the statements talk about possibilities not something that is consistent all the time.

a

explanation:

he thought hans was leaving

at least thats what i think it is

sorry if wrong