The principle of what states that hydrogen bonds can form only between certain bases in dna

There is one girl i like and i don't know how to tell her that, i have a feeling she knows but if she doesn't i don't want to make a fool out of myself how is one way to boost my confidence on asking her out

  the mississippians were considered to be  horticulturalists, which means they were

Why are people not able to skip a dive to the deepest part of the ocean