How do scientists know that dark matter exist?

a. it absorbs radio waves

b. it emits electromagnetic radiation

c. it exerts a gravitational pull on other matter

d. it blocks the light coming from other objects

Scientists cannot directly observe dark matter, but they know it exists by C, the way it exerts a gravitational pull on other matter. Most of the cosmic entities like galaxies do not have enough observable matter within them to logically exist, i.e. the amount of matter they have can’t hold the galaxy together.

c) up is the direction the magnetic force is acting on the charge.