Final answer:
Skeletal muscle fibers develop from embryonic cells called myoblasts, which are responsible for forming the multinucleated cells characteristic of mature skeletal muscle.
Step-by-step explanation:
Skeletal muscle fibers in the human body are derived from embryonic cells known as myoblasts, which originate from the mesoderm layer of embryonic tissue. These myoblasts differentiate and migrate throughout the body, where they eventually fuse to form multinucleated cells called myotubes. This fusion process is what leads to the formation of mature skeletal muscle fibers. Each skeletal muscle fiber is a long and cylindrical cell that can be quite large, with the capacity to produce the significant amounts of proteins and enzymes needed for muscle contraction. In contrast to skeletal muscle fibers, cardiac and smooth muscle cells are not multinucleate due to the absence of fusion in their myoblast precursors.
The correct answer to the student's question is B. Myoblasts.