SSC Stenographer 2022 PYQ — Question 143

The correct answer is option 4 i.e. C¹²

• ^{The relative atomic masses of all elements have been found with respect to an atom of carbon-12 (12C).}
• ^{This isotope of carbon was chosen as the reference standard for atomic mass, and its mass is defined as exactly 12 atomic mass units (u).}
• ^{The atomic masses of other elements are measured in comparison to the mass of carbon-12, which serves as a convenient baseline for expressing the relative masses of atoms and molecules}