Read the grammar rules about the past perfect. fill in the missing
words with those given in brackets.
we use the past perfect tense form to say that something had already
happened (after/before) another (past/present/future) action or a certain time
in the (past/present/future).
we form the past perfect with (have/has/had) and the (present/past)
participle of the verb (for example: gone, seen, cleaned, worked, ​