The 650 skeletal muscles in the human body contract when they receive signals from motor neurons, which are triggered from a part of the cell called the sarcoplasmic reticulum. Motor neurons tell your muscles to contract and the better you become at having those signals tell your muscles to contract, the stronger you can get.
In general, for most things, A would be correct (Any time of the day). It kind of depends on what you ar collecting the sample for. I think the earlier the better but it doesnt usually matter.
