This is a test of commonsense. Complete the next sentence:

How to make clam chowder
Purchase live hard-shell clams.
Hard-shell clams or " quahogs " like large chowder clams, littlenecks, and cherrystones should have tightly closed shells.
If you can separate the shells easily, then the clam inside is dead.
Clams that are already dead should not be purchased or, if already purchased, should be discarded. Pass a blunt knife through the two shell halves.