Which answers below best describe the definition of collision density? (mark all that are correct)

multiple answers:
you can select more than one option

a
it is the interaction rate i. e. interactions/sec.

b
it is the macroscopic cross-section times the beam intensity.

c
it is the interaction rate density i. e. interactions/cm^3-sec.

d
it is the sum of all of the macroscopic cross-sections for the material.