A scientist finds a fossil that she thinks might make a good index fossil.

A good index fossil is found in a wide geological range. Scientists look for fossils all across the world. If a new fossil is found in the same strata as an index fossil, then the new fossil's age can be correlated to time period during which the index fossil lived.

i would say b

explanation:

but i think i would need more information than that

particle   p is an electron and particle q is a neutron