The correct answer is C. Strontium-90.
Strontium-90 is a radioactive isotope of strontium that is produced by nuclear fission. It is a beta emitter and has a half-life of 28.8 years. Strontium-90 is chemically similar to calcium, and it is therefore absorbed by the body in the same way. Once it is in the body, strontium-90 can be deposited in bones, where it can cause cancer.
Radium-226 is a radioactive isotope of radium that is produced by the decay of uranium-238. It is an alpha emitter and has a half-life of 1600 years. Radium-226 is not chemically similar to calcium, and it is therefore not absorbed by the body in the same way. As a result, radium-226 is not as likely to cause cancer as strontium-90.
Thorium-232 is a radioactive isotope of thorium that is produced by the decay of uranium-238. It is a alpha emitter and has a half-life of 14 billion years. Thorium-232 is not chemically similar to calcium, and it is therefore not absorbed by the body in the same way. As a result, thorium-232 is not as likely to cause cancer as strontium-90.
Iodine-131 is a radioactive isotope of iodine that is produced by nuclear fission. It is a beta emitter and has a half-life of 8 days. Iodine-131 is not chemically similar to calcium, and it is therefore not absorbed by the body in the same way. As a result, iodine-131 is not as likely to cause cancer as strontium-90.