Which combination of alleles best describes a sex-linked trait?

Sex-limited genes are genes that exist in both genitals of sexually generating species but are manifested in only one sex and prevail 'turned off' in the other. In other words, sex-limited genes produce the two sexes to show various characteristics or phenotypes, despite having identical genotype.

Explanation:

nucleus

would be most reasonable answer tbh

before, trains worked using the steam engine. thus, it uses heat so it is crucial to apply heat balance. the steam engine absorbs energy during the stage of boiling water. so, this is the endothermic reaction. when the steam is used to work the piston, it has to release this energy through running the train. the excess energy is released as an exhaust to the chimney. this is the exothermic process because it releases energy to the surroundings.