Match List I with List II :

List I	List II
A. Incomplete dominance	I. Human skin colour
B. Co-dominance	II. Inheritance of flower colour in Antirrhinumsp.
C. Pleiotropy	III. Phenylketonuria disease in humans
D. Polygenic inheritance	IV. ABO blood groups

(A) A-II, B-IV, C-III, D-I
Incomplete dominance is observed in the inheritance of flower colour in Antirrhinum sp. (snapdragon), where the heterozygous phenotype is intermediate between the two homozygous phenotypes.
Co-dominance is exhibited by ABO blood groups in humans, where both alleles \(I^A\) and \(I^B\)
Pleiotropy occurs when a single gene influences multiple phenotypic traits. Phenylketonuria is an example of pleiotropy in humans, where a single gene mutation leads to mental retardation and a reduction in hair and skin pigmentation.
Polygenic inheritance involves traits controlled by three or more genes, such as human skin colour.
Therefore, the correct matching is A-II, B-IV, C-III, D-I.