This question tests the basic understanding of verb tenses. The simple past tense is specifically used to describe actions completed in the past. * **A is incorrect:** Present continuous describes an action happening now. * **B is correct:** The simple past tense, like ‘walked’ or ‘studied’, indicates a completed past action. * **C is incorrect:** Future simple describes an action that will happen in the future. * **D is incorrect:** Present perfect refers to an action started in the past but with relevance to the present. The main point is to know that simple past is used for completed past actions. **Core Concept:** Verb Tenses, Simple Past **Solution Strategy:** Choose the tense for completed past actions. **Option A Analysis:** The present continuous is used for ongoing actions, not completed past actions. **Option B Analysis:** The simple past is specifically used to describe completed past actions. **Option C Analysis:** The future simple is used to describe future actions, not past actions. **Option D Analysis:** Present perfect is used to link a past action to the present; not just a completed past action. **Common Mistake:** Confusing the simple past with present perfect or other tenses.