verb tense

Verb tense is the form of the verb that tells the reader when the action happens. English has three simple tenses, each with a continuous and a perfect form, and a question usually tests whether a sentence stays inside one coherent set. The simple present states a fact or a habit; the simple past reports a finished action and appears as -ed or as an irregular form such as wrote; the simple future uses will plus the base verb. The perfect forms connect two times: has finished links a past action to now, and had finished puts one past action before another past action. That last point is the one tested most — when one thing happened before another in the past, the earlier takes had. Beyond that, keep one tense inside a paragraph unless the meaning requires a shift; a sentence that slides from present to past and back for the same event is the error, not a stylistic choice.