Long-period comets come from a)the oort cloud b)the kuiper belt c)material from the asteroid belt d)particles in earth’s atmosphere don't waste my points.

Re believed to have two sources. Long-period comets (those which take more than 200 years to complete an orbit around the Sun) originate from the Oort Cloud. Short-period comets (those which take less than 200 years to complete an orbit around the Sun) originate from the Kuiper Belt.
the answer is option a the oort cloud

Its 5 points nott 50 points