Thiamine Pyrophosphate Functions as a Coenzyme in Which Reactions in the Citrate

Thiamine pyrophosphate functions as a coenzyme in which reactions in the citrate cycle?

A) pyruvate dehydrogenase and succinate dehydrogenase
B) pyruvate dehydrogenase and $\alpha$ -ketoglutarate dehydrogenase
C) malate dehydrogenase and succinate dehydrogenase
D) malate dehydrogenase and $\alpha$ -ketoglutarate dehydrogenase