Which of the following statements describes how enzymes differ from ordinary chemical catalysts?

a. enzymes are inorganic in nature.
b. enzymes catalyze select chemical reactions.
c. enzymes bind their substrates for a brief time.
d. enzymes increase the rate of a chemical reaction.

It should be b. Enzymes catalyze select chemical reactions. 

Read the sentences below in 1962, i tried to enroll as the first black student at the university of mississippi. the governor of mississippi blocked my entrance which best describes the verbs used in the sentences? o they are past tense verbs, which are often used in narrative essays o they are past tense verbs, which are not often used in narrative essays. o they are future tense verbs, which are often used in narrative essays o they are future tense verbs, which are not often used in narrative essays.

Aquantity of that isotope to decay to 1/2 of  its original value