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1. Are you waiting for the bus at the moment? Здесь используется Present continuous, потому что есть указатель времени - at the moment 
2. It snows every winter in my country. Используется Present Simple, потому что EVERY WINTER - действие повторяющееся, каждый год, каждую зиму.
3.  What is he doing now? - NOW - указатель на Present Continuous.
4. How many Noble Prize winner there had been? - Здесь уже Past Perfect
5. ??? 
6. Have you been at school yesterday? - yesterday указывает на Present Perfect

We live in a world where people are always in a hurry and don’t have enough time to eat healthy. Eating in a hurry can be harmful for the body. Buying every desired product is also risky. There are lots of products today which are genetically modified. It means that they weren’t grown in their natural environment and conditions. If we want to follow a healthy diet, we should avoid such products. Eating healthy is very important for every person. Wise people say, “Health is above wealth”. And, indeed, what can we do properly if we don’t eat. It is our natural source of energy, so it’s better to chose it carefully. For example, our body needs more vitamins and minerals but it doesn’t need much cholesterol. That’s why, it’s better to avoid using fat-containing products. We also need less sodium, which is found in salt and less sugar. I now try to eat less sweets and cakes. First of all, it can make me overweight. Secondly, it’s not good for health. Eating lots of vegetables and fruit is healthy. Other healthy and nutritious products include fish, seafood, whole grains, fat-free or low-fat milk products, lean meat, eggs, beans, seeds and nuts. However, a lot depends on every person’s body and its needs. For example, some people are highly allergic to nuts. In this case they need to cut this product out of their daily diet. Another problem is the increasing number of fast-food chains. People want to eat quickly but they don’t realize that fast-food is unhealthy. The regime of eating is also important. It means we need to eat at certain hours during the day. For example, breakfast at 8 am, lunch at 1 pm, snack at 4 pm and dinner at 6 pm. Along with eating healthy, we should try to keep fit by doing exercise, cycling, spending less time in front of the TV and not smoking.

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