If gravity alone acts to retard the expansion and nothing acts to accelerate it, the Universe is said to be closed if
I.gravity is strong enough to stop the expansion in a finite time.
II.the density of the Universe is less than the critical density.
III.the Universe is finite.

Question

If gravity alone acts to retard the expansion and nothing acts to accelerate it, the Universe is said to be closed if 
I.gravity is strong enough to stop the expansion in a finite time.
II.the density of the Universe is less than the critical density.
III.the Universe is finite.

Quizplus · Accepted Answer

The Universe is said to be closed if gravity is strong enough to stop the expansion in a finite time (I) and if the Universe is finite (III). The density being less than the critical density (II) would imply an open Universe, not a closed one.

If Gravity Alone Acts to Retard the Expansion and Nothing