Final answer:
Pantothenic acid, also known as vitamin B5, is the precursor that helps to activate Acetyl CoA. It is converted into coenzyme-A, which combines with acetyl groups derived from pyruvate to form acetyl CoA.
Step-by-step explanation:
The vitamin precursor that helps to activate Acetyl CoA is pantothenic acid, also known as vitamin B5. Pantothenic acid is converted into its active coenzyme form, coenzyme-A, which combines with acetyl groups derived from pyruvate to form acetyl CoA.