Jessie is baking a batch of popovers. which leavening agent should she use? a) baking soda b) steam c) yeast d) sourdough starter

Jessie is baking a batch of popovers. The leavening agent Jessie should use is Steam.  This is so because the volume is increased when water is converted to steam. Popovers triple in volume during baking, most of the leavening is steam. The use of Eggs is also recommended, since the egg protein causes the popover batter to stretch, hold the steam and solidify to form crusty walls.