How is the production of mercury from burning coal an environmental hazard?
a. high concentrations of mercury in the air leads to global warming.
b. mercury in water systems is transformed through biological processes into a substance that is toxic to animals.
c. mercury combines with other coal emissions in the air to produce ozone.
d. all of the above

not d ):

One function of the poly-a tail on eukaryotic mrna sequences is to the mrna be transported from the nucleus to the cytoplasm. prokaryotic mrna also has a poly-a tail. choose the best explanation of the prokaryotic poly-a tail. a. prokaryotic poly-a tails are composed of a different molecular structure compared with eukaryotic poly-a tails. b. prokaryotic poly-a tails have the same functions as eukaryotic poly-a tails, because this process is highly conserved throughout different species. c. prokaryotic poly-a tails aren't important, because prokaryotes don't have nuclei. d. prokaryotic poly-a tails have other functions,because prokaryotes don't have nuclei.