Bacteria are both evil and friend to us. why?

What is the difference between how ionic and covalent bonds form

The greenhouse effect a. something that has occurred for millions of years b. an unnatural phenomenon caused by humans that maintains earths temperature range. c. the results of the differences in the angle of the suns rays d. an unnatural phenomenon that causes heat energy to be radiated back into the atmosphere

Which kind of mutation has occurred when the codon for an amino acid is changed to a stop codon? a. a silent mutation b. a missense mutation c. a frameshift mutation d. a nonsense mutation