____ several times, the young scientist still kept ondoing his experiments.

I saw Helen in the school just now.— It ______ be Helen. She has gone to the shopping center with her sister.

How was your holiday?— It couldn’t have been _____. I just stayed in the hotel because it was raining most of the time.[ ]

I don’t mind her criticizing me, but _____ is how she does it that I object to. [ ]

Tom, don’t rub such oil into the baby’sskin, it’s not good for his health. —______.