1. which vitamin can be synthesized in significant amounts by humans and, therefore, may not be essential? a. carotenoids b. retinoids c. vitamin k d. vitamin d e. vitamin e

If you were running a marathon, which type of muscle fibers would be most useful to you? a. slow-twitch b. fast-twitch, type i a c. intermediate-twitch, type ii b d. slow-intermediate twitch, type i b select the best answer from the choices provided. a b c d