Coulomb as the SI unit of electric charge

Steps:

• Recall the SI definition: the coulomb is the charge quantity passed by a 1 ampere current in 1 second (Q = I × t).
• Evaluate choices against this: A matches exactly; B describes energy (electronvolt); C describes momentum-like quantity; D is a specific small charge value.
• Eliminate mismatches: only A aligns with the charge unit definition.
• Confirm via formula: 1 C = 1 A × 1 s, no energy or single-particle involvement.

Why A is correct:

• It directly states the official SI definition of the coulomb as Q = I × t, where 1 C equals the charge from 1 A over 1 s.

Why the others are wrong:

• B defines the electronvolt (1 eV = energy from 1 V potential on one electron).
• C incorrectly ties charge to kinetic energy at 1 m/s, which is unrelated.
• D refers to the elementary charge (≈1.6 × 10⁻¹⁹ C), not the unit itself.

Final answer: A