Question

Why is it impossible from an individual to inherit a recessive condition if only one parent is a carrier for that condition

Answer 1

Since H is dominant, well more dominant than h, it won't be recessive.

Hope this helps.

Answer 2

I added a picture of a badly-drawn cross as an example to help me explain. Let's say h is the recessive allele, in this case, that would cause a recessive condition. The heterozygous Hh parent is the carrier and they are being crossed with a homozygous dominant HH parent.

As you can see, all of the children are either homozygous dominants HH or heterozygous carriers Hh. None of the children can be homozygous recessive hh because there is not a recessive allele h to inherit from the other parent. Because H is dominant over h, the recessive condition won't be displayed.