Present Simple: My sister's friend is the best engineer at the plant.Present Continuous: My sister's friend is currently the best engineer at the plant.Present Perfect: My sister's friend has been the best engineer at the plant.Past Simple: My sister's friend was the best engineer at the plant.Past Continuous: My sister's friend was the best engineer at the plant at that time.Past Perfect: My sister's friend had been the best engineer at the plant.Future Simple: My sister's friend will be the best engineer at the plant.Future Continuous: My sister's friend will be the best engineer at the plant at that time.Future Perfect: My sister's friend will have been the best engineer at the plant.