multiple choice physiology. help anyone!?

the release of lactic acid or carbon dioxide from tissues would have which of the following effects on the radius of arterioles as well as on pre-capillary sphincters:
a.vasoconstriction and increased blood flow
b.vasodialation and increased blood flow into the capillaries
c.decrease cardiac rate
e.decrease stroke volume

during the plateau phase of myocardial contractile cell function, which of the following ions is moving in an opposite direction as compared to calcium ions
a.sodium ions
b.potassium ions
c.bicarbonate ions
d.chloride ions
e.magnesium ions