Which of the following statements about characteristics shared by all living organisms is false?
a. Single-celled organisms are not considered to be alive because although they have atoms, molecules, and a cellular structure, they don't have a tissue structure.
b. Viruses are not considered to be alive because although they have atoms, and molecules, they don't have a cellular structure.
c. Plants, bacteria, and animals all share the characteristic of responding to stimuli.
d. Plants, bacteria, and animals all share the characteristic of reproduction.