Which of the following characters are seen in sharks ?
(i) Body is streamlined and mouth is terminal .
(ii) Gill slits are not covered by operculum .
(iii) Skin is tough ,containig minute placoid scales .
(iv) many of them are oviparous .

Options

A. i and ii
B. ii iii and iv
C. iii and iv
D. I and iv

Answer

To determine which characteristics are seen in sharks, we will analyze each option one by one based on the known features of sharks (Chondrichthyes).

### Step-by-Step Solution:

1. **Analyze Option (i): Body is streamlined and mouth is terminal.**
- Sharks have a streamlined body shape which helps them move efficiently through water, reducing drag. However, their mouths are not terminal (located at the front); instead, they are ventrally located (on the underside of the head).
- **Conclusion:** This statement is **incorrect**.

2. **Analyze Option (ii): Gill slits are not covered by operculum.**
- Sharks have 5 to 7 gill slits on each side of their body, and these gill slits are indeed not covered by an operculum (a bony flap found in bony fish). This is a characteristic feature of Chondrichthyes.
- **Conclusion:** This statement is **correct**.

3. **Analyze Option (iii): Skin is tough, containing minute placoid scales.**
- The skin of sharks is tough and is covered with placoid scales, which are small, tooth-like structures that provide protection and reduce friction in the water. This is a well-known characteristic of sharks.
- **Conclusion:** This statement is **correct**.

4. **Analyze Option (iv): Many of them are oviparous.**
- Sharks exhibit various reproductive strategies, including oviparity (laying eggs) and viviparity (live birth). Many species of sharks do lay eggs, making this statement true.
- **Conclusion:** This statement is **correct**.

### Final Answer:
The characteristics seen in sharks are:
- (ii) Gill slits are not covered by operculum.
- (iii) Skin is tough, containing minute placoid scales.
- (iv) Many of them are oviparous.

Thus, the correct options are **(ii), (iii), and (iv)**.

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