Question

a mother 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

please select the best answer from the choices provided.

a
b
c
d

Explanation:

To solve this, we analyze muscle fiber types:

• Type I (slow - twitch) fibers are for endurance, not fast bursts (so A is wrong).
• Type II B (fast - twitch) fibers are used for quick, powerful, short - duration movements (like sprinting to grab a child). They respond quickly and provide speed/strength.
• There's no "type I B intermediate - twitch" (C is incorrect as this fiber type doesn't exist in standard muscle fiber classification).
• Type II A fibers are more for activities that are a mix of endurance and speed, and the description of energy delivery for II A in option D is not the main reason for a fast burst like sprinting (also, the energy delivery description for II A is not accurate for this quick - burst scenario). So the correct type for a fast, powerful burst is type II B.

Answer:

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