Student or Learner
Can I also use 'had worked' instead of 'worked' (the latter being the correct form indicated in the Answer Key):
'How long did Peter work in that office? He (to work) there for two years. Did he enjoy working there?
No, he didn't enjoy at all. That is why he came to our factory where he has working for more than a year now."
Thank you in advance!
For the question you asked about, it's only "worked." You need some other act in the past to use the past perfect.
Why does Peter know so much about manufacturing?
He had worked in a factory before becoming a teacher after university.
For the point that Matthew made, you have a problem in your last sentence: That is why he came to our factory, where he has been working for more than a year now." (Better: That is why he came to our factory. He has been working here for more than a year now.")
I'm not a teacher, but I write for a living. Please don't ask me about 2nd conditionals, but I'm a safe bet for what reads well in (American) English.
"We had been talking for a good half hour."
Quoted from for - Definition from Longman English Dictionary Online