Step 1: Understanding the Concept
Inner transition elements are the f-block elements. They are the lanthanoids (Z = 57 to 71) and the actinoids (Z = 89 to 103).
Step 2: Check each element
Sm has Z = 62, which lies in the lanthanoid series. Pd (46), Cd (48) and Au (79) are d-block elements.
Step 3: Conclusion
Only samarium is an f-block element.
Final Answer:
The inner transition element is Sm.
\[ \boxed{\text{(A) }\text{Sm}} \]