Which of the following substances is known to prevent sleep?

Chocolate is known to contain caffeine and theobromine, both of which are stimulants that can interfere with sleep. Caffeine is a well-known substance that can delay sleep onset and reduce total sleep time, while theobromine has a weaker stimulant effect but can still contribute to wakefulness. In addition to stimulants, chocolate also contains sugar, which can lead to increased energy levels and further disrupt sleep.

The other substances listed, while they may affect sleep patterns differently, are not recognized for preventing sleep in the same way that chocolate is. Cheese, milk, and beef are more likely to have calming associations, with milk containing tryptophan, an amino acid that can promote sleepiness. Understanding the effects of different foods on sleep can be crucial for individuals looking to improve their sleep quality.