The potential energy (PE) of an object is given by the formula:
\[ PE = mgh \]
where:
- \( m \) is the mass of the object,
- \( g \) is the acceleration due to gravity (approximately 9.81 m/s²),
- \( h \) is the height above a reference point.
To increase the potential energy of an Olympic ski jumper, the height \( h \) must be increased.
Therefore, the correct choice would be:
by increasing the height of the hill the jumper is skiing down.