Final answer:
Option (C), The one-day deposit rule for employment tax liabilities kicks in when an employer reaches $100,000 or more in accumulated tax liability.
Step-by-step explanation:
The amount of employment tax liability an employer must reach before the one-day deposit rule takes effect is $100,000 or more. This rule mandates that if you accumulate $100,000 or more in tax liability on any day during a monthly or semi-weekly deposit period, you must deposit the tax by the next banking day. This IRS regulation is designed to ensure that substantial tax liabilities are paid promptly.