What is involved in muscle contraction?
A. Myofibrils in the muscle shorten and lengthen to make the
muscle contract and extend.
B. Actin and myosin come in and out of the cell to make it thicker
or thinner which changes its length.
C. The gap junctions between the cells pull them closer together
which shortens the muscle.
D. The extra nuclei trigger nerves to stiffen the muscles and make
them shorter.

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explanation:

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the correct answer is: d. the saltine and pretzel are made of flour, yeast, and baking soda, and salt. the pecan contains no flour but it does contain fats. the pecan is a nut that can be consumed as a healthy snack. first of all, pecans are a source of fat (monounsaturated fat), but they provide less fat than some other nuts. pecans are a rich source of dietary fiber, manganese magnesium, phosphorus, thiamin, vitamin e…