I. Haemophilia is a sex-linked recessive disease.
II. Down's syndrome is due to aneuploidy.
III. Phenylketonuria is an autosomal recessive gene disorder.
IV. Sickle-cell anaemia is an X-linked recessive gene disorder.
(a) II and IV are correct
(b) I, III and IV are correct
(c) I, II and III are correct
(d) I and IV are correct
[NEET 2016, Phase 1]