The further we went, ____ we became.The tiredThe most tiredThe more tiredthe tireder

In this sentence, the correct choice to fill in the blank is "the more tired." Here is the detailed reasoning for the choice:

1. Understanding the Sentence Structure: The sentence structure indicates a comparative relationship, where as one action progresses (going further), another condition (feeling tired) increases.

2. Comparative Form: In English, when making comparisons regarding an increase in quality or state, we use "more" for adjectives that are not one-syllable words. "Tired" is a two-syllable adjective, which means "more tired" is the correct comparative form.

3. Elimination of Other Options:

   • "The tired": This option is incorrect as it does not follow the comparative structure required by the sentence.
   • "The most tired": This is a superlative form, which would be used if we wanted to indicate the highest level of tiredness among a group, which is not what the sentence conveys.
   • "The tireder": Although this form is technically correct, it is less common in modern English compared to "more tired."

Final Answer

The correct phrase to complete the sentence is: "The more tired."