The first step in selective breeding is to decide which individuals to breed. study the breeding habits of species. choose which characteristics to breed for. breed two different individuals to see what happens.

The correct answer would be "choose which characteristics to breed for".

Selective breeding is the process by which human breed selected animals or plants in order to produce offspring with desirable trait or phenotype. The trait or phenotype usually provide characteristics like high yield, disease resistance et cetera.

First, the desired character (such as insect resistance, high yield) is chosen for which selective breeding needs to be done.

Then, appropriate male and female animals or plants are chosen who have these traits.

The selected organisms are crossbreed to produce offspring with desired characteristics.

It is followed by inbreeding which helps in establishment and maintenance of a character in the germ line of a species.

"d.) carbon dioxide and hydrogen sulfide"