What other word from this unit has the prefix homo- and means to have two copies of the same allele

The correct answer is homozygous.

Homozygous is a term for genotype that has identical alleles for a single trait.  

An allele is a form of a gene and diploid organisms have two alleles for a given trait: one inherited from father and one for mother.

Homozygous alleles may be dominant or recessive. A homozygous dominant has two dominant alleles and expresses the dominant phenotype (expressed physical trait), while homozygous recessive has two recessive alleles and expresses the recessive phenotype.

the electromagnetic spectrum includes, from longest wavelength to shortest: radio waves, microwaves, infrared, optical, ultraviolet, x-rays, and gamma-rays.

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.