Which of the following chemical reactions is a single displacement reaction? A. 2Na + O2→
Na2O
B. 2A1 + 3Zn(NO3)2 2AI(NO3)3 + 3Zn
C. Pb(NO3)2 + 2KBr → PbBr2 + 2KNO3
D. 2Fe(OH)3 Fe2O3 + 3H2O

Which statement is true about a catalyst? a: a catalyst decreases the rate of the reaction. b. a catalyst is consumed during a chemical reaction. c. a catalyst lowers the activation energy of a reaction. d. a catalyst increases the reactant concentration during a reaction.