Figure 17-1 the Citric Acid Cycle

Figure 17-1 The Citric Acid Cycle
Use Figure 17-1 to identify the element marked with a letter. (Example: CO₂, H₂O)
-The ion(s) or molecule(s) labeled D is (are)

A) CO₂.
B) H₂O.
C) O₂.
D) H⁺.
E) 2H.