Answer:
Relative; curved; gravity.
Explanation:
According to Einstein, space and time are relative and are parts of a whole universe that has four dimensions. Masses in the universe curved space-time, and the resulting shape of space-time cause gravity.
The above theory is known as the General Relativity or General Theory of Relativity and it was published in 1915 by Albert Einstein.
Basically, it states that universe curved space-time is directly proportional to the energy and momentum of matter and radiation that is present. Thus, gravity is the universe curved space-time caused by massive objects.
