An organism containing non- identical copies of an allele responsible for a particular character is known as

The correct option is D heterozygous
Character can be defined as the visible feature of an organism that can be inherited by its progeny. If we consider the organism to be a plant, any of the visible features including the length of the stem, colour of flowers, etc. could be a character. Each character would have alternating traits- like length of the stem could be tall or dwarf, flower color could be violet or white. Diploid organisms have two copies for each trait, but they contribute a single copy to their offspring through the gamete. If both the copies received by the offspring are identical, then it is known as homozygous. If both copies received are non- identical, then it is heterozygous.

Dominant trait when present along with a recessive trait is able to suppress its expression. For example, when crossing tall pea plants with dwarf pea plants, Mendel observed that in the first filial generation, the trait for dwarfness was suppressed by trait for tallness, and hence, all the offspring in first filial generation were tall.