The answers are derived directly from the provided textbook context. For part (a), the paragraph states that dominant characters are expressed in heterozygous condition and recessive characters only in homozygous condition. For part (b), the same paragraph links homozygous to recessive expression and heterozygous to dominant expression; the terms 'identical' and 'different' alleles are inherent to the definitions of homozygous and heterozygous. For part (c), the context includes questions referring to monohybrid and dihybrid crosses, and the dihybrid example involves two traits (seed color and height), allowing the inference that monohybrid involves one trait and dihybrid involves two traits.