The disease caused by a bacterium is

Options

A. Amoebia dysentery
B. Arthritis
C. Diabetes
D. Diphtheria

Answer

To determine which disease is caused by a bacterium, we can analyze each option provided:

1. **Amoeboid dysentery**: This disease is caused by an amoeba, which is a type of protozoan, not a bacterium. Therefore, this option is incorrect.

2. **Arthritis**: This condition refers to inflammation of the joints and is not caused by bacteria. It can be due to various factors, including autoimmune diseases or wear and tear. Thus, this option is also incorrect.

3. **Diabetes**: Diabetes is primarily a metabolic disorder related to insulin levels and can have genetic factors. It is not caused by a bacterium. Therefore, this option is incorrect as well.

4. **Diphtheria**: This disease is caused by the bacterium *Corynebacterium diphtheriae*. It is a serious bacterial infection affecting the throat and nose. Hence, this option is correct.

After analyzing all the options, the disease caused by a bacterium is **D. Diphtheria**.

### Step-by-Step Solution:
1. Identify the diseases listed in the options.
2. Research the causative agents of each disease.
3. Eliminate options that are not caused by bacteria.
4. Confirm that *Corynebacterium diphtheriae* is the causative agent for diphtheria.
5. Conclude that the correct answer is D. Diphtheria.