To simplify \( 5^{10} \cdot 5^{55} \) using the Product Rule of Exponents, we apply the rule which states that when multiplying like bases, we add the exponents.
So, we have:
\[ 5^{10} \cdot 5^{55} = 5^{10 + 55} = 5^{65} \]
Thus, the simplified form is \( 5^{65} \).
None of the provided responses match this result directly. Please check the options available, but based on the computation, the answer is \( 5^{65} \).