Which of the Following Statements About Chemical Reactions Are True

Which of the following statements about chemical reactions are true? Select all that apply.

A) Chemical reactions involve the breaking of bonds between atoms in molecules, and the formation of new bonds between different groups of atoms.
B) During chemical reactions, valence electrons always move as pairs.
C) The reactants associated with a particular reaction react in different relative quantities depending on the temperature at which the reaction is being performed.
D) Chemical reactions always result in full valence shells being maintained.
E) Chemical reactions require the movement of valence electrons.