In biotechnical processes cDNA is prepared from:

Options

A. B-DNA
B. hn RNA
C. Z-DNA
D. mRNA

Explanation

To solve the question "In biotechnological processes cDNA is prepared from:", we need to understand what cDNA is and how it is formed.

### Step-by-Step Solution:

1. **Understanding cDNA**: cDNA stands for complementary DNA. It is a form of DNA that is synthesized from a messenger RNA (mRNA) template through a process called reverse transcription.

2. **Reverse Transcription**: The process of reverse transcription involves the enzyme reverse transcriptase, which synthesizes cDNA from an mRNA template. This is the opposite of the transcription process, where DNA is transcribed into RNA.

3. **Identifying the Source**: Since cDNA is synthesized from mRNA, we need to identify the correct option from the given choices that indicates the source of cDNA.

4. **Evaluating the Options**:
- Option 1: BDNA - This is a form of double-stranded DNA and is not the source of cDNA.
- Option 2: HnRNA - This stands for heterogeneous nuclear RNA, which is a precursor to mRNA but is not directly used to make cDNA.
- Option 3: ZDNA - This is another form of DNA and is not related to cDNA synthesis.
- Option 4: mRNA - This is the correct source from which cDNA is synthesized.

5. **Conclusion**: Therefore, in biotechnological processes, cDNA is prepared from mRNA.

### Final Answer:
cDNA is prepared from mRNA.