Which function will teach Karel how to spin in a circle once?

The correct answer is designed to teach Karel how to spin in a full circle. The key to understanding this lies in the concept of turning. Karel is programmed to turn left or right in increments, and each complete rotation requires a specific number of turns.

Karel can make a complete 360-degree turn by turning left four times. This is because each left turn shifts Karel's orientation by 90 degrees, and turning left four times results in a cumulative angle of 360 degrees, effectively returning Karel to the starting position.

The function that performs this action, function spin() { turnLeft(); turnLeft(); turnLeft(); turnLeft(); }, engages in the necessary four left turns to achieve the full spin. Consequently, this is the correct choice for teaching Karel to spin in a circle once.

Other options do not accomplish this full rotation. For example, turning right just once does not complete a rotation, and turning left twice only results in a 180-degree turn, which leaves Karel facing the opposite direction. Moving forward multiple steps does not affect Karel's orientation, so while it may change Karel's position, it does not achieve the objective of spinning in a circle.