Past tense review

Last week we revised the past simple, past continuous and past perfect. We stated that the past simple is used for past actions that are finished at a defined moment. The important thing is the action is completed and we know when it happened. Similarly, in the past continuous we know when the action takes place, but the action is uncomplete. So, it expresses an unfinished action at a defined moment in the past. Remember that if the time is not mentioned, the present perfect is used, mostly with periods of time or expressing personal experiences. When we referred to the past perfect I told you that it doesn't often appear in isolation, that's to say, it comes with subordinate clauses with the past simple. It expresses a past action that happened before another action in the past, I mean, it's the past in the past. The action that happened first is expressed with the past perfect, whereas the action that is nearer the present time is in the past simple. Look at these examples:

(A) Tom went to Madrid last week.
(B) The children were doing their homework at 9 o'clock.
(C) Tom has gone to Madrid.
(D) We couldn't get a hotel room because we hadn't booked in advance.

In sentence (A), the action is finished and we know when the action happened, so past simple must be used. Then in (B), at that defined time (nine o'clock) the children were in the middle of a process, they hadn't finished doing their homework, so past continuous is used. However in (C) we don't know when it happened, it may refer to a personal experience, or the result of it affects the present. In example (D), the action that happened first (book a room) is in the past perfect, and that which happened later (get a room) is in the past simple.