According to social identity theory

a. teams are never as productive as individuals working alone.
b. the most effective teams have a large number of members.
c. the team development process occurs more rapidly for heterogeneous teams than for homogeneous teams.
d. people define themselves by their group affiliations.
e. teams are less productive in performing complex tasks

D. people define themselves by their group affiliations.

answer: substrate concentration. enzymes work best when there is a high enough substrate concentration for the reaction they catalyse.

the answer is lactic acid from anaerobic respiration. the acid in lactic acid is what creates sore and burning muscles. if you think about how acid burns that will give you a clue for questions like this.