Correct statements on human chromosomes

Steps:

• Statement 1 is wrong: human body cells have 46 chromosomes total, forming 23 pairs, not 46 pairs.
• Statement 2 is wrong: gametes are haploid with 23 single chromosomes, not paired.
• Statement 3 is correct: male body cells contain one X and one Y chromosome, defining sex.
• Statement 4 is correct: each chromosome holds one long DNA molecule segmented into genes.

Why D is correct:

• Statements 3 and 4 accurately describe sex chromosome composition and chromosome structure per basic genetics definitions.

Why the others are wrong:

• A: Both 1 and 2 misstate chromosome numbers in body cells and gametes.
• B: Statement 1 incorrectly claims 46 pairs instead of 23.
• C: Statement 2 wrongly describes gametes as having paired chromosomes.

Final answer: D