**Rule**: The **Simple Past Tense** is used for a completed action that occurred at a specific time in the past. **Correct Usage**: 'in 1995' is a definite past time, so the Simple Past 'bought' is the correct choice. **Incorrect Options**: (b) 'was buying' is an ongoing action. (c) 'had bought' would need another past reference. (d) 'has bought' is a present tense.

**Rule**: The **Simple Past Tense** is used for a short, immediate reaction to another past event. **Correct Usage**: The dog 'wagged' its tail as an immediate and completed response to seeing its owner ('saw'). **Incorrect Options**: (b) 'was wagging' would imply the wagging was already in progress before it saw the owner. (c) 'had wagged' is the wrong sequence. (d) 'wags' is a present tense.

**Rule**: The **Past Perfect Continuous Tense** (had been + verb-ing) is used to emphasize the duration of an action that was in progress before another past event occurred. **Correct Usage**: 'had been playing' emphasizes the continuous performance for a specific duration ('for nearly an hour') before the singer's appearance ('appeared'). **Incorrect Options**: (a) 'played' (Simple Past) doesn't show the duration. (b) 'was playing' (Past Continuous) doesn't connect to the subsequent event as well. (c) 'had played' (Past Perfect) focuses on the completion of playing, not the continuous nature.

**Rule**: The **Simple Past Tense** is used for a completed past event that happened as a result of a prior condition. **Correct Usage**: 'flowed' is the correct verb for the single, completed event of the river overflowing. The prior condition is described in the second clause. **Incorrect Options**: (b) 'was flowing' is an ongoing action. (c) 'had flowed' would be used if another event followed. (d) 'flows' is a present tense.

**Rule**: The **Simple Past Tense** is used for a completed action in the past. The reason for the action is given in a clause with the Past Perfect. **Correct Usage**: The student 'raised' his hand. The reason was that he 'had' a question (or 'had had' a question). Simple past is clear and direct for the main action. **Incorrect Options**: (b) 'was raising' is an ongoing action. (c) 'had raised' would imply he raised his hand before he had the question. (d) 'raises' is a present tense.

**Rule**: The **Simple Past Tense** is used for a completed past action, which is then commented on. **Correct Usage**: 'broke' is the simple past action. The second clause ('which was very disappointing') describes the speaker's feeling about that past action. **Incorrect Options**: (b) 'was breaking' is an ongoing process. (c) 'had broken' would be used if this action happened before another past action. (d) 'breaks' is a present tense.

**Rule**: This sentence shows a sequence of past events. The earlier event is in the Past Perfect, and the later event is in the **Simple Past Tense**. **Correct Usage**: The doctors changing the medication ('had changed') happened first. The result, which came later, was that the patient 'felt' better. **Incorrect Options**: (b) 'was feeling' would imply an ongoing process of feeling better. (c) 'had felt' would illogically place the feeling before the cause. (d) 'feels' is a present tense.

**Rule**: This sentence describes a past ongoing action and the prior reason for it. The **Past Continuous** describes the ongoing action. **Correct Usage**: The ground 'was shaking' (the ongoing event). The reason for it was the prior long duration of rain ('had been raining'). **Incorrect Options**: (a) 'shook' is a short, completed action. (b) 'had shaken' is the wrong sequence. (d) 'shakes' is a present tense.

**Rule**: The **Simple Past Tense** is used to ask questions about completed actions at a specific (though unstated) time in the past. **Correct Usage**: 'When did you last get...?' is the standard structure for asking about the most recent occurrence of a past event. **Incorrect Options**: (b) 'were, getting' asks about an ongoing action at a specific past moment. (c) 'had, gotten' would need another past reference. (d) 'do, get' is a present tense.

**Rule**: The **Simple Past Tense** is used for an action that was completed at a specific, stated time in the past. **Correct Usage**: The phrase 'last year' is a definite time in the past, so the Simple Past 'wrote' is the correct choice to describe the completed action. **Incorrect Options**: (b) 'was writing' (Past Continuous) implies the action was in progress, not completed. (c) 'had written' (Past Perfect) would be used if this action happened before another past action. (d) 'had been writing' (Past Perfect Continuous) would emphasize the duration of the writing process.