Architecture Puzzler #169

You’re at a construction site and about to climb the builder's extension ladder to the parapet 20 feet (6.1 meters) above. You notice the base of the ladder is about 5 feet (1.5 meters) from the wall. Do you leave it there or do you ask the builder to move it out from the wall another 18 inches (46 centimeters) or so?

Cavitating pumps are pumps that:
a) Are used for pumping concrete
b) Are shaking
c) Switch back and forth from supply to return