The answer is d- Presence of RBCs.

The pink color of urine sample during physical examination is known as hematuria, which is the presence of red blood cells (RBCs) in the urine. Hematuria can be seen in various conditions such as urinary tract infections, kidney stones, bladder or kidney tumors, and glomerulonephritis.

When RBCs are present in the urine, they may cause the urine to appear pink, red, or brown. The color of the urine may depend on the amount of blood present and how long it has been in the urine. For example, if there is a small amount of blood in the urine, it may appear pink or light red. However, if there is a large amount of blood in the urine, it may appear dark red or brown.

Diagnosis of hematuria requires a thorough evaluation by a healthcare professional, including a physical examination, urine analysis, and imaging studies. Treatment of hematuria depends on the underlying cause.

References:
1. Hematuria. National Kidney Foundation. https://www.kidney.org/atoz/content/hematuria
2. Hematuria. Mayo Clinic. https://www.mayoclinic.org/symptoms/hematuria/basics/definition/sym-20050740