Photosynthesis ceases when leaves wilt, mainly because
\begin{equation}\begin{array}{l}{\text { (A) the chlorophyll in wilting leaves is degraded. }} \\ {\text { (B) accumulation of } \mathrm{CO}_{2} \text { in the leaf inhibits enzymes. }} \\ {\text { (C) stomata close, preventing } \mathrm{CO}_{2} \text { from entering the leaf. }} \\ {\text { (D) photolysis, the water-splitting step of photosynthesis, }} \\ {\text { cannot occur when there is a water deficiency. }}\end{array}\end{equation}