a Paul was making a phone call when I went into his office.
b Paul had some coffee first and then he made some phone calls.
c Paul had made twenty phone calls by the time he left the office for the day.
a As it was getting dark, the boys decided to go home.
b When it got dark, all the lights in the park went on creating a beautiful atmosphere.
c By the time the boys decided to return home, it had gotten so dark that they needed a torch to find their way.
a Dr Stephens was performing an experiment while his students were watching him.
b Dr Stephens had performed a lot of experiments before he made an important discovery.
c Two weeks ago Dr Stephens performed an experiment with the help of some university students.
a The baby fell asleep, as soon as we put her in her bed.
b As the baby was falling asleep, she was making some funny sounds.
c The baby had fallen asleep by the time he got home and he didn’t want to wake her up.
a Laura had read the report many times before she gave it to her boss.
b While Laura was reading the report, her computer started making strange noises and stopped working.
c Laura read the report, switched off her computer and went home.