Research that is based on observation only, without an attempt to alter or change an event, is called ______________ research.

Which water sources contain water under air pressure that is released when required by the system?

A. Reservoirs B. Gravity tanks C. Suction tanks D. Pressure tanks

The phase of the cardiac cycle when the ventricles contract is called _________________

A. systole C. diastole B. ischemia D. fibrillation