Final answer:
The CR for the lateral projection of the ankle should enter the ankle joint at the center of the joint space, between the medial and lateral malleoli.
Step-by-step explanation:
For the lateral projection of the ankle, the central ray (CR) should enter the ankle joint at the center of the joint space. The CR should be directed perpendicular to the image receptor (IR) and aimed at the midpoint between the medial and lateral malleoli. This ensures that the entire ankle joint is included in the image.