Which best describes why heat pumps are reversible? a. they can heat and cool an indoor space. b. they involve a metal expanding or contracting against another. c. they combust and can also add coolant. d. they allow a piston to move up and down.

A. They can heat and cool an indoor space.

nucleic acid molecules are incredibly complex, containing the code that guarantees the four different nucleotide units comprise dna, the nucleic acid of interest to the genealogist. and one of four nitrogen-containing molecules called nucleotides

the correct answer in apex is tissue development, i know because i just had this question