Among the following organisms which is a completely non-parasitic form?

Options

A. Sea anemone
B. Tapeworm
C. Leech
D. Mosquito

Explanation

To determine which organism among the given options is a completely non-parasitic form, let's analyze each option step by step:

### Step 1: Understand the definition of a parasite
A parasite is an organism that obtains nutrients at the expense of another organism (the host), often causing harm to it. Parasites can be classified into two types: ectoparasites (living on the outside of the host) and endoparasites (living inside the host).

### Step 2: Analyze the options
1. **C. anemone**: This organism belongs to the phylum Coelenterata (now known as Cnidaria). Sea anemones are primarily sessile and do not rely on a host for nutrients. They capture prey using their tentacles but do not harm a host organism in the parasitic sense.

2. **Tapeworm**: Tapeworms are endoparasites that live inside the intestines of their hosts, absorbing nutrients from the host's digested food. They are harmful to the host.

3. **Leech**: Leeches are ectoparasites that attach to their hosts and suck blood. They are considered parasites as they derive nutrients from the host.

4. **Mosquito**: Mosquitoes are also ectoparasites that feed on the blood of their hosts. They can transmit diseases and are harmful to their hosts.

### Step 3: Conclusion
Among the options provided, the only organism that is completely non-parasitic is **C. anemone**.

### Final Answer:
**C. anemone** is the completely non-parasitic form among the given organisms.

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