What statement is true concerning the hydrostatic lubrication of plain bearings?

Correct Answer: Option A — An outside pressure source is required for lubrication and full-film lubrication is present at any shaft speed.

Hydrostatic lubrication involves supplying lubricant under external pressure to the bearing clearance space. This creates a full-film condition that supports the load even when the shaft is stationary or rotating at very low speeds, effectively eliminating metal-to-metal contact regardless of the shaft's rotational velocity or hydrodynamic film development.