[单选题]
Which is not a correct defg )v2aqzb2t;qlj c1qf-(9a1m*m jnxt inkp*s- gutapm 3l/:)i cition or equation for water potential?
A. The sum of the solute and pressure potential of a solvent
B. ψ$_w$ = ψ$_s$ + ψ$_p$
C. The direction that water will move through a semipermeable membrane
D. The potential energy of water per unit volume
