What does the phrase 'expansion limits' refer to?

The phrase 'expansion limits' specifically pertains to the area that robots are allowed to occupy during gameplay. In the context of rules and field specifications, these limits define how much a robot can extend or occupy space beyond its starting dimensions.

When robots are designed, teams must adhere to these guidelines to ensure fair play, as overstepping these limits can provide an unfair advantage. Understanding these constraints is crucial in strategizing robot design and tactics, as teams must ensure their robots can perform effectively within the allowable area while complying with the game's regulations.

The other choices focus on different aspects of robot construction and design, such as maximum size, height during gameplay, and gear ratios, which are not directly related to the concept of expansion limits.