Выберите правильную временную форму (Present Perfect or Past Simple):
1. He was (interested / has been interested) in scientific research since he entered the university.
2. When did you (install / have you installed) the new equipment in the laboratory?
3. They (didn't give / haven't given) the explanation of these strange facts yet.
4. They (determined / have determined ) the main properties of the substance.
5. He (has just made / just made) a discovety in physics.
6.They (didn't receive / haven't received ) any good results when they worked with this type of equipment.