Explanation:
As you can see in the picture below, this is a dihybrid cross with a twist.
We can accomplish that mutually parentages are heterozygotes for both characters because the genotypes are
9 unicorns with curly tails (shown in green)
3 with straight tails (shown in red)
3 curly tales trait carriers with no tail (shown in dark blue)
1 straight tail trait carriers with no tail ( shown in light blue)
If this was an ordinary case of the dihybrid cross, we would get a 9:3:3:1 phenotype ratio.
However, since the first trait, the presence of the tail, is affecting the other trait, the trait texture, the ratio is altered.
of the offspring (genotypes tt C_ and tt SS) has no tail, therefore we cannot observe the texture of the tail (some of the tailless individuals have Curly alleles -blue squares marked with green, some of them have Straight alleles -blue square marked with red ).
Therefore, the altered ratio is curly tails,
straight tales,
tailless