Coulomb defined as charge from current and time

Steps:

• Recall that electric charge is the quantity of electricity, measured in coulombs.
• Know the fundamental definition: charge Q equals current I times time t, so Q = I × t.
• Identify units: current in amperes (A), time in seconds (s), thus coulomb (C) = A × s.
• Confirm no other base units define it directly in SI system.

Why A is correct:

• The SI definition states 1 coulomb is the charge passing through a conductor when a current of 1 ampere flows for 1 second (Q = It).

Why the others are wrong:

• B: Ampere and volt define power (watt), not charge.
• C: Volt and ohm define current (ampere), not charge.
• D: Volt and second relate to magnetic flux (weber), not charge.

Final answer: A