The answer is (c), Radium-226 (emits alpha particles and gamma rays).
The major types of radiation emitted during radioactive decay are alpha particles, beta particles, and gamma rays.
Alpha particles have a high mass and move slowly through air. Alpha particles lack the energy to penetrate the outer dead layer of skin.
Beta particles are fast moving electrons emitted during radioactive decay. Beta particles travel considerable distances in air but can be reduced or stopped by a layer of clothing or by a few millimeters of a substance, such as aluminum
Gamma rays are weightless packets of energy called photons. Gamma rays often accompany the emission of alpha or beta particles from a nucleus. Several feet of concrete or a few inches of lead may be required to stop gamma rays.