Which statement best explains why the atmosphere is considered an open system? a there is no definite boundary separating it from outer space. b energy and matter can enter and leave. c its molecules can move freely, without resistance. d it can accept an unlimited amount of energy.

Match the following terms describing electrical events with the correct phases of the cardiac cycle. the ventricular muscle cells depolarize at the start of this phase. during this phase, na+ entry through the funny channels causes the pacemaker potential of sa nodal cells to gradually become less negative until it reaches threshold. the ventricular muscle cells repolarize right before this phase. the cytosolic concentration of calcium in the contractile cells of the ventricle is highest during this phase. a. isovolumetric relaxation b. ventricular ejection c. isovolumetric contraction d. ventricular filling

Earthquakes a. created the rock in arches utah b. can be caused by volcanic eruptions c. are caused by tsunami waves d. wear mountains down into hills

Do anyone know who mrs leddy is from duval charter if so me on the homework for 40 points