The correct option is Two/too.

Let us break down the logical and grammatical reasoning step-by-step to understand why this option is correct:

1. Analyzing the first blank: "After playing _________ hours of tennis..."
In this context, we need a word to specify the number of hours played. The word "Two" is a numeral representing the number 2. The word "Too" means "also" or "excessively", which does not fit grammatically before the noun "hours" here. Therefore, the first blank must be filled with "Two" (or "two").

2. Analyzing the second blank: "...I am feeling _________ tired to walk back."
Here, we need an adverb to modify the adjective "tired" to indicate an excessive degree that leads to a certain result (being unable to walk back). The adverb "too" fits perfectly in the structure "too [adjective] to [verb]" (e.g., "too tired to walk"). The numeral "two" does not make sense in this position. Therefore, the second blank must be filled with "too".

3. Combining the answers:
Putting it all together, the sentence becomes: "After playing two hours of tennis, I am feeling too tired to walk back." This corresponds exactly to the option Two/too.