What Is the Meaning of the Word Spacetime

What is the meaning of the word spacetime?

A) It is a mental framework for keeping track of numbers in Newtonian physics.
B) Space and time form a two-dimensional region where physics takes place.
C) The term has no special meaning; it's just a fancy way to sound important when talking about physics.
D) It is the combined treatment of space and time in the theory of relativity.
E) It is the idea that observers will always measure the same locations and times of events.