The diagram illustrates a force $F$ acting at $90^\circ$ to a bar, at a distance $d$ from point $P$. Which pair of changes would lead to the greatest increase in the moment of the force $F$ about the point $P$?
- Ahalving $F$ and halving $d$
- Bhalving $F$ and doubling $d$
- Cdoubling $F$ and halving $d$
- Ddoubling $F$ and doubling $d$