How does a molecule differ from an atom?

The table shows dates and appearance of index fossils. which rock layers can be dated most precisely? a) a layer containing both a fossil 4 and a fossil 3 b) a layer containing both a fossil 2 and a fossil 3 c) a layer containing both a fossil 1 and a fossil 4 d) a layer containing both a fossil 1 and a fossil 2

How can antibodies "remember" a particular bacterial invader or "antigen" on that invader?

If your blood becomes too concentrated with iona, what will happen to the red blood cells