The vitamin that is not soluble in water is

Options

A. Vitamin `B_1`
B. Vitamin `B_2`
C. Vitamin `B_6`
D. Vitamin D

Explanation

To determine which vitamin is not soluble in water, we can follow these steps:

### Step 1: Understand Vitamin Solubility
Vitamins are classified based on their solubility into two main categories: water-soluble and fat-soluble. Water-soluble vitamins include the B-complex vitamins and vitamin C, while fat-soluble vitamins include vitamins A, D, E, and K.

### Step 2: Identify Water-Soluble Vitamins
The water-soluble vitamins are:
- B-complex vitamins (such as B1, B2, B6, etc.)
- Vitamin C

These vitamins dissolve in water and are not stored in the body; excess amounts are excreted through urine.

### Step 3: Identify Fat-Soluble Vitamins
The fat-soluble vitamins are:
- Vitamin A
- Vitamin D
- Vitamin E
- Vitamin K

These vitamins do not dissolve in water and can be stored in the body's fatty tissues.

### Step 4: Answer the Question
Since the question asks for the vitamin that is not soluble in water, we can conclude that the answer is **Vitamin D**.

### Final Answer
The vitamin that is not soluble in water is **Vitamin D**.

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