Plague is transmitted by______.

Explanation

**Step-by-Step Solution:**

1. **Identify the Disease**: The question asks about the transmission of the plague, which is an infectious disease caused by bacteria.

2. **Understand the Causative Agent**: The plague is caused by a bacterium known as *Yersinia pestis*. While the bacterium itself is the causative agent of the disease, it is not directly responsible for its transmission.

3. **Identify the Vectors**: The transmission of the plague primarily occurs through vectors. In this case, the main vectors are fleas that are infected with the plague bacteria.

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