Read the given statements characterizing certain types of animals. Select the option which correctly exemplifies each of these types.
(i) Animal having external gills
(ii) Animal having internal gills
(iii) Animal showing tracheal respiration
(iv) Animal revealing buccopharyngeal respiration

Options

A. `{:("(i)",(ii),(iii),(iv)),("Prawn","Arenicola","Unio",Fish):}`
B. `{:("(i)",(ii),(iii),(iv)),("Necturus","Unio","Prawn","Frog):}`
C. `{:("(i)",(ii),(iii),(iv)),("Pila","Arenicola","Unio","Toad"):}`
D. `{:("(i)",(ii),(iii),(iv)),("Necturus","Pila","Milipede","Toad"):}`

Explanation

To solve the question regarding the types of animals based on their respiratory structures, we will analyze each statement and identify the correct examples for each type of respiration.

### Step-by-Step Solution:

1. **Animal having external gills**:
- External gills are projections from the body surface and are not enclosed by the body wall. They are typically found in certain larval forms of amphibians and some aquatic organisms.
- Among the options provided (Prawn, Necturus, Pila, Necturus), Necturus is the correct answer. Necturus is a genus of aquatic salamanders that possess external gills during their larval stage.

2. **Animal having internal gills**:
- Internal gills are covered and protected by soft skin folds, such as the interbranchial septum or operculum. They are found in certain mollusks and some aquatic organisms.
- The options provided are (Arnicola, Unio, Arnicola, Pila). Pila, which is the scientific name for the apple snail, is known to have internal gills (also called tinnidium) that allow it to respire in water.

3. **Animal showing tracheal respiration**:
- Tracheal respiration involves a system of air-filled tubes (trachea) that facilitate gas exchange in certain arthropods, including insects and myriapods.
- The options given are (Unio, Prawn, Unio, Millipede). The correct answer is Millipede, as it is a group of arthropods that utilize tracheal respiration.

4. **Animal revealing buccopharyngeal respiration**:
- Buccopharyngeal respiration occurs through the lining of the mouth and is characteristic of certain amphibians, particularly frogs, when they are not submerged in water.
- The options provided are (Fish, Frog, Toad, Toad). The correct answer is Toad, as it also exhibits buccopharyngeal respiration.

### Final Answers:
- (i) Necturus (external gills)
- (ii) Pila (internal gills)
- (iii) Millipede (tracheal respiration)
- (iv) Toad (buccopharyngeal respiration)