In humans, the trait for brown eyes is dominant (B) and blue eyes is recessive (b). Which alleles would be present in the gametes of a human if that human is heterozygous for eye color?

Question

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Most plant and animal cells are diploid. The term diploid means "double" or "two". When we refer to a cell as being diploid, we mean that the cell contains pairs of chromosomes. For example, human cells have 46 chromosomes organized in 23 pairs. 
A gamete is a sex cell (sperm in males, eggs in females). Gametes are formed through meiosis - a process in which the number of chromosomes is halved. So, for example, a human gamete would contain half of the 46 chromosomes, which is 23 chromosomes. We call gametes haploid, which means "single". This is because the chromosomes are no longer in pairs. 
During sexual reproduction, these haploid gametes (a sperm and an egg) unite with each other to create a diploid, fertilized egg cell, called a zygote.
In this question, we are asked which alleles would be present in a gamete. 
The different forms of a gene are called alleles. In this question, the two alleles discussed are the dominant allele for eye color in humans - brown, which we repesent with a capital letter (B) - and the recessive  allele for eye color in humans - blue, which we represent with a lowercase letter (b). 
Because the parent is heterozygous (they have both the dominant and recessive alleles for eye color), and a gamete is a haploid cell, half of the parent's gametes will contain the dominant allele while the other half will contain the recessive allele.

In Humans, the Trait for Brown Eyes Is Dominant (B)