(Answer) (d) Chemical reaction rates vary with the conditions of the reaction, but nuclear decay rates do not.
Rate of a chemical reaction refers to rate of formation of products from reactions during a chemical reaction. The rates of chemical reactions depend on various factors such as temperature, pressure, concentration of reactants, presence of catalyst etc. For this reason, chemical reaction rates vary with the conditions of the reaction.
Nuclear decay rate refers to the constant ratio of the number of atoms of radioactive nucleus that decay during a certain interval of time to the total number of radioactive atoms at the beginning of the time interval. Nuclear decay rates are constant and do not vary with the conditions of the reaction.