Final answer:
To jump higher in a halfpipe competition, snowboarders must increase momentum and manage their trajectory and body position, rather than merely shifting body weight or changing the snowboard's width.
Step-by-step explanation:
To jump higher during a halfpipe competition, snowboarders need to perform several actions that involve physics principles. The correct option for jumping higher is not explicitly provided in the options a), b), c), or d), as each could influence the performance in different ways depending on the context. However, typically, snowboarders would need to increase their momentum and use their body to manage the trajectory and angle of their jump.
When preparing to jump, a snowboarder must generate a sufficient amount of upward force. This can involve crouching down before the lip of the halfpipe and extending their legs forcefully to gain height. Additionally, the snowboarder would shift their body weight based on the phase of the jump: while approaching the jump, they might lean slightly forward to maintain balance and momentum; in the air, they adjust their center of mass to control their rotation and landing; during landing, they absorb the impact with flexed knees to maintain control.
In the context of the given options, increasing the angle of their snowboard (option c) could be part of the strategy for gaining height, as a steeper angle on the halfpipe's transition can translate to more vertical momentum. However, this should be carefully managed to prevent loss of control.