Step 1: Understanding the Concept:
Hepatic function and biliary clearance testing in small animal clinical biochemistry.
Step 2: Detailed Explanation:
Evaluating liver function tests (LFTs) in canines:
1. A. Sulfobromophthalein (BSP) Clearance Test: A true test of hepatic excretory function; assesses hepatic blood flow, hepatocyte uptake, intracellular conjugation, and biliary excretion of an injected dye ($< 5\%$ retention at 30 min is normal in dogs).
2. C. Estimation of Serum Bilirubin (Total, Direct, Indirect): Standard marker of hepatic uptake, conjugation capacity, and post-hepatic biliary patency.
3. Trypsin tests assess exocrine pancreatic function (EPI); malabsorption tests assess intestinal villous enteropathy.
Thus, tests A and C only directly assess liver function.
Step 3: Final Answer:
Hence, the liver function tests are A and C only, matching option (C).