Explanation

When restricted stock units (RSUs) vest:

• The compensation expense has already been recognized over the vesting period
• At vesting date, the company transfers the value from equity (specifically, from "additional paid-in capital" or similar equity accounts) to common stock
• This is essentially a transfer between balance sheet accounts (within equity)
• No new compensation expense is recorded at vesting
• The cash flow statement is typically unaffected by this non-cash transaction

The correct answer is A: a transfer between two balance sheet accounts. The accounting entry involves moving the value from one equity account to another, typically from additional paid-in capital to common stock.