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XIV. Identify the one underlined word or phrase that must be changed to make the sentence correct.
1. If someone came into the store, smile and say, "May I help you?"
2. If you try these cosmetics, you look five years younger.
3. If you do not understand what were written in the book, you could ask Mr. Pike.
4. I will come to meet Mr. Pike and tell him about your problems if you didn't solve them yourself.
5. Sam will not graduate unless he doesn’t pass all the tests.
6. If there isn’t enough food, we couldn't continue our journey.
7. Unless you pour oil on water, it will float.
8. You have to take a taxi home if you want to leave now.
9. If anyone will phone, tell them I'll be back at 11:00.
10. We can hire (A) a minibus (B) if (C) there will be (D) enough people.