According to the passage, a worker primarily works for ______.

A．One improves muscular action consciously.
B．One performs simple actions without working.
C．One always knows what his muscles are doing.
D．One’s muscles are used only to the extent necessary for each action they perform.

A．She also prefers to exercise in the morning.
B．It’s important to warm up before exercising.
C．The man should start running daily.
D．The man should continue his exercise program.