Consider the following statements
For osmoregulation in aquatic medium
1. A freshwater fish has to drink water continuously
2. A marine bony fish has to drink water continuously
3. A freshwater fish produces copious urine, which is hypo-osmotic to blood
4. A marine fish produces scanty urine, which is hypo-osmotic to blood
Which of the statements given above is/are correct?

Options

A. 1 only
B. 4 only
C. 1 and 4
D. 2 and 3

Answer

To determine which statements about osmoregulation in aquatic environments are correct, let's analyze each statement step by step.

### Step 1: Analyze Statement 1
**Statement:** A freshwater fish has to drink water continuously.
**Analysis:** Freshwater fish live in an environment where the concentration of salts in the water is lower than the concentration of salts in their body fluids. To maintain osmotic balance, they do not need to drink water continuously; instead, they absorb water through their skin and gills. Therefore, this statement is **incorrect**.

### Step 2: Analyze Statement 2
**Statement:** A marine bony fish has to drink water continuously.
**Analysis:** Marine bony fish live in a salty environment where the concentration of salts is higher than in their body fluids. To counteract dehydration, they actively drink seawater and excrete the excess salts through their gills and produce small amounts of urine. Thus, this statement is **correct**.

### Step 3: Analyze Statement 3
**Statement:** A freshwater fish produces copious urine, which is hypo-osmotic to blood.
**Analysis:** Freshwater fish do produce a large volume of urine to eliminate excess water, but this urine is not hypo-osmotic to their blood; it is actually more dilute (or less concentrated) than their blood. Therefore, this statement is **incorrect**.

### Step 4: Analyze Statement 4
**Statement:** A marine fish produces scanty urine, which is hypo-osmotic to blood.
**Analysis:** Marine fish produce a small amount of urine due to their need to conserve water. The urine they produce is indeed more concentrated (hyperosmotic) compared to their blood, not hypo-osmotic. Therefore, this statement is **incorrect**.

### Conclusion
After analyzing all statements:
- Statement 1: Incorrect
- Statement 2: Correct
- Statement 3: Incorrect
- Statement 4: Incorrect

Thus, the only correct statement is Statement 2.

### Final Answer
The correct statements are: **Only Statement 2 is correct.**