Answer:
gravitational force
Explanation:
We have four types of fundamental forces in nature
1) Electromagnetic force: It is of either repulsive or attractive type of force and this depends on distance between charges and polarity of charge.
2) Strong and weak nuclear force: this is also of attractive or repulsive type of force and it only depends on distance between two nuclei.
3) Gravitational force: It depends on the mass of the objects and it is only attraction type of force.
so here all matter in universe attract each other only due to gravitational force because all other forces are of both type i.e. attraction and repulsion both.
so correct answer will be
gravitational force
