Question

A plants can have either brown (B) or red (b) leaves. Brown is the dominant trait is a plane as a genotype Bb which best describes the plant. A. Homozygous with brown leaves. B. Heterozygous with red leaves C. Homozygous with red leaves. D. Heterozygous with brown leaves

Answer 1

D.  Heterozygous with brown leaves
It is heterozygous because the alleles are differen. Bb have different alleles, B and b. As opposed to homozygous which have same alleles, B and B or b and b.
Since B is dominant in the gene expression, and B represents brown, the dominant trait will mask the recessive one, b, and you will have a brown leaf.
Hope this helps. 

Answer 2

Answer: The correct answer is-  D. Heterozygous with brown leaves.

According to the information given in the question, brown leaves (depicted by 'B' allele) is a dominant trait over red leaves ( depicted by 'r' allele), which is a recessive trait.

A dominant trait ( depicted by capital letter allele) is the one that masks the expression of a recessive trait ( depicted by small letter allele).

There can be two possible genotypes for brown leaves that is BB ( homozygous dominant, as it is having both the dominant alleles) and Bb ( heterozygous dominant, as having two different alleles that is 'B' and 'b').

Thus, plant with genotype Bb can be said as Heterozygous ( having two different alleles) with brown leaves.