The Optimal Length (L_o) of a Skeletal Muscle Cell Is

The optimal length (L_o) of a skeletal muscle cell is:

A) the length at which the muscle can generate its maximum tetanic tension.
B) the shortest length the muscle can achieve while attached to bone, because the amount of overlap between thick and thin filaments is maximal then.
C) generally the length attained when the joint it crosses is fully extended.
D) the only length at which any tension can be generated by the muscle cell.
E) the length at which thin filaments from opposite sides of a sarcomere overlap.