What increases the effect of centrifugal force on the vehicle when driving round bends?

You answered correctly. The effect of centrifugal force increases when you drive faster or when the curve is sharper (with a smaller radius). This means that higher speed and tighter bends both make the sideways force on your vehicle stronger, which can lead to loss of control if you are not careful. Higher tyre pressure, however, does not increase centrifugal force; it's mainly about speed and curve tightness. Remember, reduce your speed before entering tight bends to keep the vehicle stable.