Final answer:
The a. Deaver retractor is the tool most commonly used to lift the edge of the liver during surgery due to its shape and size specifically designed for this purpose.
Step-by-step explanation:
The retractor most commonly used to lift the liver edge during surgical procedures is the Deaver retractor. This type of retractor is specifically designed to hold back portions of the liver to provide surgeons with better visibility and access to the operative field. It has a distinctive, large, and curved shape that conforms well to the liver's contour, making it an essential tool in abdominal surgeries. While other retractors like the Richardson, Bookwalter, and Weitlaner are useful in their respective applications, the Deaver retractor is particularly suited to manipulate and retract the liver.