In human males all the chromosomes are paired perfectly except one. This/these unpaired chromosomes is/are :
(i) large chromosome (ii) small chromosome (iii) Y chromosome (iv) X chromosome

Options

A. (i) and (ii)
B. (iii) only
C. (ii) and (iv)
D. (iii) and (iv)

Explanation

To solve the question regarding which chromosome is unpaired in human males, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Chromosome Structure in Humans:**
- Humans have a total of 23 pairs of chromosomes, making a total of 46 chromosomes.
- Out of these, 22 pairs are autosomes (non-sex chromosomes), and the 23rd pair consists of sex chromosomes.

2. **Identify the Sex Chromosomes:**
- In human males, the sex chromosomes are represented as XY.
- The X chromosome and the Y chromosome are not identical and do not form a perfect pair.

3. **Analyze the Options Given:**
- (i) Large chromosome: This is not specific and does not refer to the sex chromosomes.
- (ii) Small chromosome: Again, this is not specific and does not refer to the sex chromosomes.
- (iii) Y chromosome: This is one of the sex chromosomes and is unpaired with another Y chromosome.
- (iv) X chromosome: This is the other sex chromosome and is also unpaired with another X chromosome.

4. **Conclusion:**
- The unpaired chromosomes in human males are the X and Y chromosomes. Therefore, the correct answer includes both the Y chromosome and the X chromosome.

### Final Answer:
The unpaired chromosomes in human males are (iii) Y chromosome and (iv) X chromosome.

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