Concept:The correct pattern is “so + adjective + that” to express result.Explanation:“He is so poor that he cannot pay his bills.”The structure “so…that” means “to such a degree that…” and connects the cause and result.“Too” would require “to” (e.g., “too poor to pay”), not “that.”“Very” and “rather” do not fit before “that” in this cause-and-result pattern.Answer:A. so