When two chromosome resemble each other in size shape and the kind of heriditary information carried they are said to be

The two chromosomes in a homologous pair are very similar to one another and have the same size and shape. Most importantly, they carry the same type of genetic information: that is, they have the same genes in the same locations.

"do a testcross with a homozygous recessive plant."

a covalent bond, specfically triple bond