Option 1: Brain cancer. This option is incorrect because the radioactive Strontium-90 primarily affects the bones and not the brain. It does not cause brain cancer.
Option 2: Skin cancer. This option is correct. Radioactive Strontium-90 exposure can lead to skin cancer. The radiation emitted by Strontium-90 can cause damage to the skin cells and potentially result in the development of cancer.
Option 3: Lung cancer. This option is incorrect. Strontium-90 primarily affects the bones and does not directly cause lung cancer.
Option 4: Bone cancer. This option is not the correct choice. Radioactive Strontium-90 specifically impacts the bones, and its radiation can increase the risk of developing bone cancer.
In conclusion, the correct answer is option 2, as Strontium-90 exposure has been linked to an increased risk of skin cancer.