In Guard Cells, _____ Is the Dominant Osmoticum in the Morning

In guard cells, _____ is the dominant osmoticum in the morning, and ______ is the dominant osmoticum in the afternoon.

A) Cl^-; sucrose
B) malate; K⁺
C) K⁺, malate
D) sucrose; K⁺
E) K⁺; sucrose