Answer
a) TTAA, TtAA, TTAa, TtAa
b) Test cross with a ttaa plant.
c) Based on Punnett squares between each genotype in parts a) & b), they are, respectively 100% tall and axial; 50/50tall, all axial; all tall, 50/50 axial; 50/50 for both tall and axial. This is a prediction, not a cross with actual plants.
d) Compare the predictions in c) and the results of b) to see which match up to identify the unknown genotype.
Work Step by Step
This question is really not very complex--it asks you to review the use of test crosses and to design one for a dihybrid cross and to describe how to interpret the results.