Which of the following statements correctly describes a change in matter responses

a. a chemical change is indicated when two compounds are mixed, leading to the production of gas bubbles.
b. a chemical change is indicated when two compounds are mixed, leading to the production of gas bubbles.
c. a physical change is indicated when two compounds are mixed and form a new substance.
d. a physical change is indicated when two compounds are mixed and form a new substance.
e. a chemical change is indicated when a substance undergoes a phase change from gas to a solid.