What are main agencies involved in spreading of germs?

The earths core is made up mainly of what 2 substances? 2. like an egg, earth has a core, a layer surrounding the core, and a thin, hard outer layer. which layers of the earth match the layers of an egg?

What do we call an individual that has inherited two identical alleles for the same trait? a.homozygous b.heterozygous c.monozzygous

What is an example of a scientific question that galileo could not have answered with out this new tool?