When cells want to store up energy will they add or delete a phosphate group

they will add.

Explanation:

When a cell has energy available it can store small amounts of energy by adding a phosphate group to ADP molecules producing ATP molecules. The energy stored in ATP is released when ATP is converted to ADP and a phosphate group.

what statement best describes the difference between the sympathetic and parasympathetic nervous systems?

the sympathetic nervous system prepares the body for intense physical activity and is often referred to as the fight-or-flight response. the parasympathetic nervous system has almost the exact opposite effect and relaxes the body and inhibits or slows many high energy functions.