What type of line does this composition contain

The observations of hooke and van leeuwenhoek documenting the existence of microscopic cells formed the basis of what important theory? a. the cell theory stating that all living things are composed of cellsb. the theory of spontaneous generation, which held that life forms could arise spontaneouslyc. the theory of chemotherapy, or use of antimicrobials to destroy pathogenic organismsd. the germ theory of disease and causative agents

Facilitates growth and change in neurons and the migration of neurons to different sites in the brain

How does the study of genetic disorders such as pku biologists understand normal alleles?