What are the 3 types of variables ?

The influenza virus cause the flu, but not other diseases. why?

The response is the basis for vaccination. primary secondary tertiary none of the above

Cattle with brown fur and cattle with white fur will produce a reddish roan calf . when examined closely, the calf show about an even number of brown hairs and white hairs that give a reddish appearance when viewed from far away. the fact that both the brown fur allele and the white fur allele are expressed equally in the offspring is an example of