How do plants return nitrogen to the soil

With regard to enzymes, key is to lock as a) substrate is to activation energy eliminate b) product is to substrate. c) enzyme is to active site. d) substrate is to active site.

Why do some dna fragments move farther than others during gel electrophoresis? a. because their shapes are different b. because they are different types of molecules c. because the samples are different colors d. because their masses are different

Which description shows competition in an environment? an organism that feeds on some food an organism that finds a place to sleep three organisms of the same species living in an area three organisms battling over limited resources