The right answer is A. glucose.
The term "oxidation" more broadly refers to a reaction in which a reagent loses one or more electrons.
The oxidation of the glucose molecule occurs during glycolysis by losing its electrons and transmitting them to NAD + to give NADH:
Glucose + 2 ADP + 2 Pi + 2 NAD + -----> 2 pyruvate + 2 ATP + 2 H2O + 2 NADH.