Which of the following isotopes is used for treatment of cancer ?

Options

A. `K^(40)`
B. `Co^(60)`
C. `Sr^(90)`
D. `I^(131)`

Answer

To determine which isotope is used for the treatment of cancer, we can analyze the given options one by one:

1. **Potassium-40 (K-40)**: This isotope is a naturally occurring radioactive isotope of potassium. It is not commonly used in cancer treatment.

2. **Cobalt-60 (Co-60)**: This isotope is well-known for its use in radiation therapy for cancer treatment. Cobalt-60 emits gamma rays, which can be directed at cancerous tissues to destroy them. This makes it a primary choice in the medical field for treating various types of cancer.

3. **Strontium-90 (Sr-90)**: While this isotope is used in some medical applications, such as in the treatment of certain eye diseases, it is not primarily known for cancer treatment.

4. **Iodine-131 (I-131)**: This isotope is used in the treatment of thyroid cancer and hyperthyroidism. It is effective for specific types of cancer but is not as widely used as cobalt-60 in general cancer treatment.

After analyzing the options, we find that the correct answer is:

**Cobalt-60 (Co-60)** is the isotope used for the treatment of cancer.

### Step-by-step Solution:
1. **Identify the options given**: Potassium-40, Cobalt-60, Strontium-90, and Iodine-131.
2. **Understand what isotopes are**: Isotopes have the same atomic number but different mass numbers.
3. **Evaluate each option**:
- Potassium-40: Not used for cancer treatment.
- Cobalt-60: Used for cancer treatment via gamma rays.
- Strontium-90: Not primarily used for cancer treatment.
- Iodine-131: Used for specific types of cancer (thyroid).
4. **Conclude which isotope is primarily used for cancer treatment**: Cobalt-60 is the most recognized isotope for this purpose.