Which statement about reaction rates is true?

a. a catalyst slows down the reaction rate.
b. changing the surface area affects the reaction rate.
c. changing the amount of reactants will not change the reaction rate.
d. changing the temperature cannot speed up a reaction rate.

Which of these statements best explains why space exploration should be encouraged? it prepares humans to live without oxygen. it dispel myths about objects in space. it prevents comets and asteroids from striking earth. it creates technology to absorb harmful radiations in space.