Which of the following isotopes is most dangerous to Homo sapiens?

Explanation

Strontium-90 (Sr-90) is a radioactive isotope of strontium, and it is indeed considered dangerous due to its potential health risks associated with exposure to ionizing radiation. One of the main concerns with strontium-90 is its chemical similarity to calcium. When released into the environment, strontium-90 can be absorbed by living organisms, particularly in the form of strontium ions, which can replace calcium ions in bones. As a result, it tends to accumulate in bone tissues, where it can irradiate the bone marrow and cause damage to blood-forming cells.