Which of these are families of elements?

a.
metals and noble gases

b.
shells and nonmetals

c.
properties and rare earth elements

d.
metalloids and atoms

Were does condensation occur? a) hydroshereb) lithosherec) boishered) atmosphere

Lactase is essential for digesting lactose in milk. this enzyme is specific for this sugar. why? molecules and active sites vary in size; only properly sized molecules can fit.there is a precise compatibility between the active site and the lactose molecule.specificity refers to the action of the enzyme, such as hydrolysis, and relatively few molecules can be hydrolyzed.reaction-specific enzymes assume a fit by folding around the most numerous substrate molecules.

Which is an example of a vestigial structure? a: paw of a lionb: wing of a birdc: appendix of a humand: tail of a cat(i think it's a but i'm not sure)