How many statements are correct with respect to chrysophytes ?
(i) They are found in the marine environment , freshwater organisms are very rare.
(ii) In diatoms , the cell wall form two thick overlapping shells which fit together as in a soapbox .
(iii) The cell membranes of diatoms are embedded with silica and accumulation of them over billions of years is referred to as "diatomaceous earth "
(iv) Diatoms are the chief " Producers" In the oceans .

Options

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

Answer

To determine how many statements are correct with respect to chrysophytes, let's analyze each statement one by one:

1. **Statement (i)**: "They are found in the marine environment, freshwater organisms are very rare."
- This statement is **incorrect**. Chrysophytes, which include diatoms, are found in both freshwater and marine environments. Freshwater organisms are not very rare; in fact, many chrysophytes thrive in freshwater.

2. **Statement (ii)**: "In diatoms, the cell wall forms two thick overlapping shells which fit together as in a soapbox."
- This statement is **incorrect**. In diatoms, the cell wall is made up of two **thin** overlapping shells (valves) that fit together like a soapbox, not thick shells.

3. **Statement (iii)**: "The cell membranes of diatoms are embedded with silica and accumulation of them over billions of years is referred to as 'diatomaceous earth.'"
- This statement is **correct**. Diatoms have cell walls made of silica, and the accumulation of these silica-rich remains over time results in deposits known as diatomaceous earth.

4. **Statement (iv)**: "Diatoms are the chief 'Producers' in the oceans."
- This statement is **correct**. Diatoms are indeed one of the primary producers in marine ecosystems, contributing significantly to the ocean's primary productivity.

Now, let's summarize the correctness of each statement:
- Statement (i): Incorrect
- Statement (ii): Incorrect
- Statement (iii): Correct
- Statement (iv): Correct

Thus, **two statements (iii and iv) are correct** with respect to chrysophytes.

### Final Answer:
**2 statements are correct.**