Complete the sentences with the Past Perfect Simple or the Past Perfect Continuous forms.

1
a Trevor ...... (live) in this town for 20 years before he found out that his next door neighbour used to be a famous actress.
b Trevor ..... (know) his next door neighbour for twenty years before he found out she used to be a famous actress.
2
a Vladimir ...... (sneak) out of the house secretly at night for months before he was finally caught.
b Earlier that night, Vladimir ..... (sneak) out of the house without waking his parents.
3
a The security guard ........ (sleep) for hours when the office was broken into.
b The security guard was fired because he ........ (sleep) through the burglary.