in the 19th century, german physician robert koch proposed four postulates that serve to
a. explain how the immune system functions in terms of its ability to prevent future infection following experience combating a particular disease agen
b. prove that llving organlsms can spontaneously arise from nonliving matter
c. prove a causal relationship between a microorganism and a disease
d. disprove that llving organisms can spontaneously arise from nonliving matter
e. differentiate prokaryotes from eukaryotic cells