___________ he has limited technical knowledge, the old worker has a lot of experience

Scientists are convinced _____ the positive effect oflaughter _____ physical and mental health．

Please don’t make so much noise. I hear the speaker very well.

She is a strong-willed woman and not once _____ in to any difficulty in her life. [ ]

Someone is knocking at the door. Who may it be–It ______ be Tom. He is still in the school.