Correct Option: A

The curie (symbol Ci) is a non-SI unit of radioactivity, named ‘in honour of’ Pierre Curie. It was originally defined as “the quantity or mass of radium emanation in equilibrium with one gram of radium (element)”, but is currently defined as: 1 Ci = 3.7 × 1010 decays per second after more accurate measurements of the activity of 226Ra.