Amother sprints across the yard to grab her small child before he enters the street. the mother is using her a. type i a slow-twitch muscle fibers that provided her with a fast burst of movement b. type ii b fast-twitch muscle fibers that respond quickly and provide her with speed and strength c. type i b intermediate-twitch muscle fibers that respond quickly because they are delivered energy aerobically d. type ii a fast-twitch muscle fibers that act rapidly because they are delivered energy anaerobically

The answer is "B. type II B fast-twitch muscle fibers that respond quickly and provide her with speed and strength".

Fast-twitch muscles separate into two classes: moderate fast-twitch (type IIa) and fast-twitch (type IIb or IIx). Moderate fast-twitch muscles are thicker, faster to contract, and destroy more quickly than slow-twitch. Fast-twitch, the most ground-breaking and least in continuance, are initiated when the body nears greatest effort.  

Here's the means by which it works: During aerobic activities, for example, running or swimming, slow-twitch fibers are the first to contract. At the point when the slow-twitch fibers wind up drained, fast-twitch fibers start to assume control.  

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