The correct answer is: oxaloacetate
Anaplerotic reactions are chemical reactions that form intermediates that can be used in the further steps of metabolic pathways. These reactions are very important, because it is crucial for the cell to regulate concentrations of TCA cycle metabolites and intermediates.
The reaction in which pyruvate is converted to oxaloacetate is catalyzed by pyruvate carboxylase and it occurs in mitochondria. Also, pyruvate can be converted to L-malate, in a similar way.