used with reference to another action or a point of time in the past.it is, therefore,incorrect to say,"He had read Moby Dick.",unless the context makes it clear what time point the sentence is related to. 2.When describing one event following another in the past, we can show their relationsby using the past perfect for the earlier event,or else we can use the past tense for both,and rely on the conjunction (e.g.after,when)to show which event took place earlier.for example,we can either say: Example: When the teacher had left the room,the children started talkingused with reference to another action or a point of time in the past. it is, therefore, incorrect to say, “He had read Moby Dick.”, unless the context makes it clear what time point the sentence is related to. 2. When describing one event following another in the past, we can show their relationsby using the past perfect for the earlier event, or else we can use the past tense for both, and rely on the conjunction (e.g. after, when) to show which event took place earlier. for example, we can either say: Example: When the teacher had left the room, the children started talking