How does human activity impact Earth's systems such as deforestation, urbanization, desertification, erosion, air and water quality, and
alternating the flow of water? ***Please use full sentences.
Please answer

Which statement best describes the relationship between an allele and a gene? question 1 a. an allele is a variation of a gene that can be expressed as a phenotype. b. an allele is the part of a gene that attaches to messenger rna molecules. c. an allele is a segment of a dna molecule that controls replication of a gene.