Correct answer: D
A pollen is where male gametes are produced and so the number of chromosomes, as we are talking about gametes, is n. This means that the grain of pollen will only have a copy of each gene, and therefore only one allele for each gene - one S, and one T or t. So, the possible combinations are ST and St.
Because the dark box is blending in with the shadows, however the white box is bright and easier to see
Simple organic molecules can be organized into much longer, more complex molecules.
Sun which produces sunlight