Robert Rescorla showed that classical conditioning works best when the conditioned stimulus allows for a reliable prediction of the occurrence of the unconditioned stimulus.

This statement is true. Rescorla's studies demonstrated the importance of contingency in classical conditioning. When the conditioned stimulus (CS) is consistently paired with the unconditioned stimulus (US), and only when the CS is a reliable predictor of the US, strong learning occurs. In contrast, when the CS and US are not reliably associated, learning is weak.