Genotype result of double fertilization
IMO, the question is unclear

The question is unclear to me. I understand we expect a triploid nucleus plus a diploid zygote (double fertilization) but I don't understand what (TTT + TTt), TT means.


Which book did the question come from?
Is there any preamble to this question?


Double fertilization

I am not so used to thinking about double fertilization in plants. In short, two pollens are involved. One fertilize a haploid gamete from the mother and the other fuse with two haploid gamete (polar nuclei) from the mother (triple fusion) resulting in a triploid "individual".

In my below answer, I am assuming that any two polar nuclei can fuse with the pollen. I am not sure this is true. If it is systematically polar nuclei resulting from the same meiosis II (that is they have the same parent cell after meiosis I), then t story is a little different.

How I understand the question

In my understanding, we are talking about a single locus with two alleles T and t. Both pollens are T. The mother is Tt.

Answer

There are two possible gametes from the female side T and t. Only one possible gamete from the male side T. Therefore, the diploid zygote is either


$\frac{1}{2}$ TT
$\frac{1}{2}$ Tt


, where the numbers indicate probabilities

Now, for the triploid nucleus resulting from the fertilisation of two polar nucleus from the mother and one pollen grain can be either


$\frac{1}{4}$ TTT
$\frac{1}{2}$ TtT or tTT
$\frac{1}{4}$ ttT


Now, I have no idea how that matches to the possible answers as I don't understand the notation.