What do we mean by inflation?

Question

What do we mean by inflation?

Answer

A) the expansion of the universe that we still observe today

B) the sudden release of photons when a particle and antiparticle annihilate one another

 C) a sudden and extremely rapid expansion of the universe that occurred in a tiny fraction of a second during the universe's first second of existence

D) quantum fluctuations by high speed, relativistic particles in a state of false vacuum that caused disturbances in the space-time continuum leading to the process described in the question to which this answer refers