To form the past participle of a verb, add the ending-ed to the base form. (But note that manycommon verbs have irregular past participle forms.)The past participle is used in the following circumstances:
Has the gas chromatograph been fixedyet?
The gas chromatograph was fixed on Monday.
We had the gas chromatograph fixedlast week.
The recently fixed gas chromatograph isbroken again.
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