Correct Answer (Detailed Explanation is Below)
C.
Angstrom
Detailed Explanation
Angstrom is the smallest among the listed units. One angstrom equals 10⁻¹⁰ metre, whereas one centimetre equals 10⁻² metre. Small units such as
nanometre, angstrom and picometre are commonly used for microscopic and atomic measurements. In competitive examinations, carefully compare the powers of ten before selecting the answer.