18. A human has

O 21
• 22
pairs of chromosomes.
© 23:
O 24

23. This statement is incorrect. Humans have a total of 23 pairs of chromosomes, not 22.

There seems to be some confusion in the provided information. Humans typically have 23 pairs of chromosomes, for a total of 46 chromosomes. Each pair consists of two chromosomes, one inherited from each parent. If further clarification is needed, please let me know.