Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): The dose of X-rays and most other ionizing radiations is measured as Roentgen units. Reason (R): One Roentgen is that dose of radiation, which produces one electrostatic unit of charge in one cm3 volume under a standard set of conditions. In the light of the above statements, choose the most appropriate answer from the options given below: