Ineed to know the answer of this 2 question

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

Why are scientists concerned about the depletion of the ozone levels in the stratosphere?

Which of the following is the earliest era of earth's geologic time scale? cenozoic mesozoic precambrian paleozoic