(choose all that apply)
which factors make it hard for eastern europe to improve the quality of its water?

a. eutrophication
b. carbon credits
c. outdated systems
d. raw water quality
e. unskilled workers

Choose the best definition of allele. a. one of several possible versions of a gene, which each produce a different phenotype b. an organism that's purebred for a given trait c. the process of fertilizing a plant with pollen from another plant d. a set of genes that are located on the same chromosome and so are tightly linked