To What Does the Phrase "Synchronous Rotation" for an Astronomical

To what does the phrase "synchronous rotation" for an astronomical object (e.g., planet or moon) refer?

A) It has a rotation rate that is precisely maintained (e.g., 23 h 56 m 4.096 s for Earth) .
B) For an object in an elliptical orbit, the rotation rate increases and decreases to match the changes in its orbital speed.
C) It completes precisely one rotation around its own axis for every orbit (1-to-1 spin-orbit coupling) .
D) It has any rotation period that is in simple proportion to its orbital period (1-to-1 spin-orbit coupling, 3-to-2 spin-orbit coupling, etc.) .