# Which of the following is most likely cause for wider opening of stomata?

$\begin{array}{1 1}(A)\;\text{Atmosphere outside the stomata is becoming less saturated}\\(B)\;\text{Secretion of salt molecules by adjacent guard cells is taking place} \\(C)\;\text{Water molecules enter the guard cells}\\(D)\;\text{The night temperature is going to fall}\end{array}$

Water molecules enter the guard cells
Hence (C) is the correct answer.