Alimentary canal of earthworm is

Options

A. a) Incomplete and straight
B. b) complete but coiled
C. c) complete and straight
D. d) Incomplete and highly branched

Explanation

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the structure of the alimentary canal of an earthworm. We need to determine if it is complete or incomplete, and whether it is straight or coiled.

2. **Definition of Alimentary Canal**: The alimentary canal is a continuous tube that runs from the mouth to the anus, responsible for digestion and absorption of food.

3. **Complete vs. Incomplete Alimentary Canal**:
- An **incomplete alimentary canal** has only one opening (either a mouth or an anus).
- A **complete alimentary canal** has two openings (a mouth and an anus).

4. **Analyzing the Earthworm's Alimentary Canal**:
- Earthworms have both a mouth and an anus, indicating that their alimentary canal is **complete**.

5. **Structure of the Alimentary Canal**:
- The earthworm's alimentary canal consists of the following parts in order: mouth, pharynx, esophagus, crop, gizzard, intestine, and finally the anus.
- Observing the arrangement of these parts, we can see that they form a straight line rather than a coiled structure.

6. **Conclusion**:
- Since the alimentary canal of the earthworm is complete (has both mouth and anus) and straight, the correct answer is **Option C: complete but straight**.