Which of these is an example of acceleration?

a bicyclist turning around a corner

a car travelling south with its cruise control set

a bus travelling north at 25m/s

a helicopter waiting to take off

A bicyclist turning around the corner

Step-by-step explanation:

Upon taking a corner, the bicyclist experiences a net external force, centripetal force, which produces acceleration. The acceleration tends toward the center since the bicycle travels in a circular path. The bicycle accelerates along it's circular path.