Largest blood vessel of earthworm's body is

Options

A. a) Ventral blood vessel
B. b) Dorsal blood vessel
C. c) Sub-neural blood vessel
D. d) Lateral oesophageal vessel

Explanation

To solve the question regarding the largest blood vessel in the earthworm's body, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Question**: The question asks for the largest blood vessel in the earthworm's body. We need to identify which of the given options is correct.

2. **Review the Options**: The options provided are:
- A) Ventral blood vessel
- B) Dorsal blood vessel
- C) Subneural blood vessel
- D) Lateral esophageal vessel

3. **Identify the Blood Vessels**:
- The **ventral blood vessel** runs along the belly side of the earthworm.
- The **dorsal blood vessel** runs along the back side, above the intestine.
- The **subneural blood vessel** is located below the nerve cord.
- The **lateral esophageal vessel** is associated with the esophagus.

4. **Locate the Dorsal Blood Vessel**:
- The dorsal blood vessel is positioned just above the intestine and is located along the mid-dorsal line of the earthworm.

5. **Determine the Size and Function**:
- The dorsal blood vessel is not only the largest blood vessel in the earthworm but also the thickest. It is responsible for transporting blood from the posterior to the anterior end of the body.

6. **Identify Additional Features**:
- The dorsal blood vessel has a pair of valves at each end and is often referred to as the "true heart" of the earthworm.

7. **Conclusion**: Based on the information gathered, the largest blood vessel in the earthworm's body is the **dorsal blood vessel**. Therefore, the correct answer is **Option B**.

### Final Answer:
**The largest blood vessel of the earthworm's body is the dorsal blood vessel (Option B).**