The Enzyme That Converts Pyruvic Acid into Acetyl-CoA Requires Vitamin

The enzyme that converts pyruvic acid into acetyl-CoA requires vitamin B₁, also called thiamine. Vitamin B₁ has to be taken in through the diet of an individual. At what phase would cellular respiration come to a halt without B₁?

A) glycolysis
B) preparatory reaction
C) citric acid cycle
D) electron transport chain
E) carbon fixation