The correct arrangement is: (1) (D), (B), (A), (C)

(D) "I had resigned myself to sitting at home assuming" introduces the context or background information. It sets the stage by explaining the speaker's initial expectation or assumption.

(B) "that walking aggravates knee pain" follows logically from the previous sentence, explaining the assumption or belief that walking worsens the knee pain, contributing to the narrative.

(A) "but it was a great relief to find out that nine minutes" introduces a change or a revelation in the speaker's perspective, indicating that their earlier assumption was incorrect.

(C) "of brisk walk is beneficial for alleviating the condition" completes the narrative by providing the positive outcome or solution to the issue, explaining that brisk walking can be beneficial for the condition.