The substance given to caner patients in order to activate their immune system and destroy the tumour is

Options

A. histamine
B. interleukin
C. `alpha`-interferon
D. morphine.

Explanation

To answer the question regarding the substance given to cancer patients to activate their immune system and destroy tumors, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Purpose**: The question asks for a substance that activates the immune system in cancer patients and helps destroy tumors.

2. **Review the Options**: The options provided are:
- A. Histamine
- B. Interleukin
- C. Alpha-interferon
- D. Morphine

3. **Analyze Each Option**:
- **Histamine**: This is a compound involved in local immune responses and does not specifically activate the immune system against tumors.
- **Interleukin**: While interleukins are important in immune responses, they are not specifically known for direct tumor destruction in cancer therapy.
- **Alpha-interferon**: This is a type of interferon that is produced by the immune system in response to pathogens and is known to enhance the immune response against tumors.
- **Morphine**: This is a pain relief medication and does not have a role in activating the immune system or destroying tumors.

4. **Select the Correct Answer**: Based on the analysis, the substance that is specifically used to activate the immune system and help destroy tumors in cancer patients is **C. Alpha-interferon**.

### Final Answer:
The substance given to cancer patients in order to activate their immune system and destroy the tumor is **C. Alpha-interferon**.