If the pedigree below is for an autosomal recessive characteristic, which individuals are definitely heterozygous?

A) I-1, I-2, II-2, II-4, II-5
B) I-1, I-2, I-4, III-1
C) I-1, I-2, II-4, II-5, III-1
D) II-2, II-4, II-5, II-3
E) II-2, II-4, II-5, III-1