Read the following statements and choose the correct set of statements :
$(a)$ In sickle cell anaemia the mutant haemoglobin molecule undergoes polymerisation under high oxygen tension
$(b)$ Thalassemia is a qualitative problem
$(c)$ Turner's syndrome,Klinefelter's syndrome are common examples of chromosomal disorders.
$(d)$ Haemophilia is a sex-linked recessive disease

• A
  $(a), (b), (c)$ and $(d)$ only
• B
  $(a), (c)$ and $(d)$ only
• C
  $(c)$ and $(d)$ only
• D
  $(a)$ and $(b)$ only