1. By use of a differential pressure compression tester, it is determined that the No. 3 cylinder of a nine-cylinder radial engine will not hold pressure after the crankshaft has been rotated 260° from top dead center compression stroke No. 1 cylinder. How can this indication usually be interpreted? A. A normal indication. B. Exhaust valve blow-by. C. A damaged exhaust valve or insufficient exhaust valve clearance.