## Core Concept
Diatoms are a type of algae found in both freshwater and marine environments. They are known for their cell walls made of silica, which give them a unique characteristic. Diatoms play a significant role in aquatic ecosystems and are used in various industrial applications.

## Why the Correct Answer is Right
The correct answer, although not directly provided, relates to understanding which statement about diatoms is not true. Generally, diatoms are known for their contribution to the world's oxygen supply through photosynthesis, their use in filtration and as a food source for aquatic animals, and their cell walls are indeed made of silica.

## Why Each Wrong Option is Incorrect
- **Option A:** Without specific details on option A, we can infer that if it states a true characteristic of diatoms, such as their role in producing oxygen or their silica cell walls, it would be correct and not the answer.
- **Option B:** Similarly, if option B presents an accurate feature of diatoms, like their habitat or industrial use, it wouldn't be the correct answer to this question.
- **Option C:** This option might discuss another valid aspect of diatoms, such as their fossil record (diatomite) or their importance in aquatic food chains.
- **Option D:** Given that the question asks for the statement that is NOT true about diatoms, option D likely presents an inaccurate or less accurate statement regarding diatoms compared to the others.

## Clinical Pearl / High-Yield Fact
Diatoms are crucial in the production of diatomaceous earth or diatomite, which has various applications, including filtration and as an insecticide. Their unique characteristic of having silica cell walls makes them useful in several industrial processes.

## Correct Answer Line
**Correct Answer: D.**