Final answer:
A recessive trait can only be expressed in the homozygous condition, whereas a dominant trait can be expressed in the heterozygous condition. Hence, the assertion is correct, but the reason is incorrect.
Step-by-step explanation:
The assertion and reason are referring to the principles of genetics. In Mendelian genetics, traits are defined as recessive or dominant. The assertion (A) is correct: a recessive trait can only be expressed in the homozygous condition, meaning when an organism has two copies of the recessive allele (e.g., aa). The reason (R) is incorrect: a dominant trait can indeed be expressed in the heterozygous condition, which means an organism only needs one copy of the dominant allele (A) to exhibit the dominant trait (e.g., Aa or AA). So, the answer is (b) (A) is correct and (R) is incorrect.
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