You will be given a definition of a task first, then some input of the task.
In this task, you are given a context and four options. Each option is a suggested ending for the context. You should read the context and pick the best ending for the context. Please answer with "A", "B", "C", and "D".

[header] How to build leg muscles [title] Train two or three times a week. [step] Many people think that to build muscle you have to train every day, but that's not the case. Muscles get bigger when they get small " breaks " in training, and get stronger when they build up again during rest days. <sep> (A) [substeps] Try to make sessions slightly shorter each week. This can be anywhere from five to eight sessions. (B) There are several ways to improve leg muscles : [substeps] Use a tape measure or pencil to measure the distance between your lower thighs and upper thighs. Line up the measuring tape and record the distance so you can accurately find the number of steps you need to put on each leg before starting to create a " plan ". (C) So don't exercise the same muscle groups two consecutive days. Rotate muscle groups so you're training your arms, back, chest, and other areas on the days you aren't working out your legs. (D) [substeps] One study found that those who train three times a week increased leg strength and ultimately reduced the cost of physical activity as a result. If you lose a few pounds, you can increase the amount of you workout routine.
Output:
C