Which one is found only in RNA and not in DNA ?

Options

A. Cytosine
B. Adenine
C. Uracil
D. Guanine.

Answer

To answer the question "Which one is found only in RNA and not in DNA?", we can follow these steps:

### Step 1: Identify the nitrogenous bases in DNA and RNA.
- DNA contains four nitrogenous bases: adenine (A), thymine (T), cytosine (C), and guanine (G).
- RNA contains four nitrogenous bases as well: adenine (A), uracil (U), cytosine (C), and guanine (G).

### Step 2: Compare the bases of DNA and RNA.
- In DNA, thymine (T) is present, while in RNA, thymine is replaced by uracil (U).
- The bases adenine (A), cytosine (C), and guanine (G) are present in both DNA and RNA.

### Step 3: Identify the unique base in RNA.
- Since uracil (U) is present in RNA but not in DNA, it is the base that is found only in RNA.

### Conclusion:
- The correct answer is **uracil**.