Consider the following reaction of β-D-galactose with isopropylamine and explain why only a small amount of acid is used for the formation of an N-glycoside.

• A. A trace amount of acid is used to keep the amine mostly in its neutral, nucleophilic form while still allowing protonation of the sugar's oxygen.
• B. The acid is only needed to catalyze the ring-opening of the sugar, so a small amount is sufficient.
• C. A small amount of acid is used to prevent the formation of side products by minimizing sugar degradation.
• D. A trace amount of acid is used because the reaction is pH-sensitive and requires strongly basic conditions to proceed.