Malic acid is found in apples. Given suitable conditions, which substance reacts with just one of the $-\text{OH}$ groups in the malic acid molecule?
- A$\text{Cr}_2\text{O}_7^{2-} / \text{H}^+(aq)$
- B$\text{Na}(s)$
- C$\text{NaOH}(aq)$
- D$\text{PCl}_5(s)$