According to this passage, more than haft of a person's body is composed of ______.

A．the muscular sense is more important than any other sense
B．muscular sense involves automatic perception
C．there are many more than 500 involuntary muscles in the body
D．muscle tissue is inflexible

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