In which situation is a deduction of 0.30 points applied?

A deduction of 0.30 points is applied in a situation where a gymnast squats on landing. This deduction reflects the severity of this error as it indicates a significant lack of control during the dismount or landing phase of a skill. Squatting on landing suggests that the athlete was unable to maintain proper body alignment and balance, which is a critical aspect of executing skills effectively in gymnastics.

Additionally, other options indicate less severe errors. A slight hop on landing could result in a smaller deduction due to being a minor adjustment for balance, while feet being closer than hip width apart might not necessarily demonstrate a loss of control significant enough to warrant a full 0.30 point deduction. Extra trunk movements can also signify some loss of form, but typically do not incur the same level of deduction as a squat on landing does. Thus, the context of each scenario highlights why squatting on landing specifically merits a 0.30 point deduction, as it points to a more pronounced error in execution and control.