In the copolymerization of acrylonitrile and styrene, if we use a 1:1 mixture of the two monomers, what is the composition of the initial polymer formed and what are the average sequence lengths of the resulting polymer chains?

A) The composition of the initial polymer is a random copolymer, and the average sequence lengths of the resulting polymer chains are determined by the reactivity ratios of acrylonitrile and styrene.
B) The composition of the initial polymer is a block copolymer, and the average sequence lengths of the resulting polymer chains are equal for acrylonitrile and styrene monomer units.
C) The composition of the initial polymer is a graft copolymer, and the average sequence lengths of the resulting polymer chains are determined by the concentration of initiator used.
D) The composition of the initial polymer is a alternating copolymer, and the average sequence lengths of the resulting polymer chains are random due to statistical distribution of monomer units during polymerization.