сделать задание по английскому! Are these sentences RIGHT or WRONG?

1. An operator can know how to use the telephone system. An operator may know how to use the telephone system. An operator should know how to use the telephone system.
2. I suggest we should buy a mobile telephone to stay in touch. I suggest we bought a mobile telephone to stay in touch. I suggest to buy a mobile telephone to stay in touch.
3. If Tom called leave me a message. Should Tom called leave me a message. Must Tom called leave me a message.
4. You should deal with the calls promptly in the morning but I see that they are not answered. You should have dealt with the calls promptly in the morning but I see that they are not answered. You should be dealing with the calls promptly in the morning but I see that they are not answered.

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When summer vacation coming to an end, we begin to prepare for school. it is no accident that it is the first day of the school year marks the day of knowledge, it is called so. after all, what school? this is the place where we learn a lot of new and interesting things about the world, the mysteries of nature and ourselves. we gain knowledge and skills that will be useful to us throughout life, and learn to understand the beauty, to communicate with people to develop their talents. the first of september - joyful day when, after the summer holidays, we return to school to learn new skills and meet friends. this is the day when empty without school students again filled with children's voices and the rustle of notebooks. again joyfully ringing school bell, announcing the beginning and end of the lesson. i still remember how one day on september mom brought me to school the first time. i remember it was a little scary and insanely fun! so many children, flowers, music, new neat form how many unexplored ahead! i knew i was an adult, not some kind ditsadkovets, and with trepidation expecting what will be my first lesson. on this day, we go to school especially good, funny, with bouquets of flowers. our teachers, head teachers, the director said many warm parting words, we want academic excellence. in my opinion, this is good - to begin the school year with the holidays, it charges a good mood on the difficult but interesting training routine.