What type of reaction is A + B → AX

Which of these would be caused by a chemical change? a) the formation of lava. b) sedimantary rock layering over time. c) metamorphic rock forming from igneous. d) metamorphic rock eroding to form sedimentary rock.

When a septic tank backs up a goes in to clean it out

The chemical bond connecting one nucleotide with the next one along the nucleic acid chain is called a