How does a catalyst work?

a. by increasing the temperature of a chemical reaction
b. by decreasing the pressure of a chemical reaction
c. by increasing the concentration of reactants in a reaction
d. by decreasing the activation energy of a reaction

D or A I think but I could be wrong

the glands which are associated with each description is given below:

pancreas - is an endocrine and exocrine gland that secretes juices with enzymes for digestion. salivary glands- with protection and digestion in the mouth. liver- secretes bile for digestion.   lachrymal glands - secrete tears to moisten eyes and protect them from particles and infection.   sweat gland -regulates water, salt, and temperature. oil glands - to form a protective barrier on the skin.   goblet cells - secrete mucus for protection.