Q: What must a chemical reaction overcome before starting?\nOptions:\n- (A) PV=nRT\n- (B) heat or cold\n- (C) reactants\n- (D) energy barrier\n- (E) Dehydration\n- (F) harmful substances\n- (G) resistance\n- (H) temperature
Let's think step by step below.

User
All chemical reactions require activation energy to get started. Activation energy is required to overcome the energy barrier. All chemical reactions must first overcome the energy barrier.
Thus, the answer is (D).
Assistant