The workers (paint) the walls. Мой ответ

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

At fifteen - seventeen years, is incredibly difficult to choose the one unique profession that then you will give many years of life, will improve their skills. But I was lucky, I knew from early childhood that will artist. My grandfather and father - artists. I love to watch them work. Father - a painter, and his father - the schedule. I have not decided what I will give preference I like arts and crafts. I myself have manufactured jewelry boxes, and then I paint their magical designs or uncomplicated scenes from folk life. It attracts me and monumental painting murals in churches. These majestic creatures survived the centuries and now have a lot to tell us about their creators, their genius and skill. This artist loved summer - in his bright palette raznotsvete without dimming centuries of paint. And then I worked ascetic lines of his drawings are stingy and impeccably accurate, there is no external prettiness, but they are perfect, a few strokes create a whole world. Attracts me and the work of theater artists, decorators, their skill never ceases to amaze and delight. That appears on the scene an old overgrown garden, a lake with swans, an ancient castle or gay village street. All this created a skilled and talented hands of professional artists. But to become a master, you must work very hard, to develop his own style, otherwise we should not take on such a complex and wonderful work. I hope that you fall and you suddenly become famous - did not succeed. We must work hard every day, hone your style and skills, only then something can get. But first we must decide. And it is very difficult, I want to try myself in everything. Father says I scatter. And I'm looking for a way to select it, and then regret not achieve excellence in the profession. Otherwise, it is nothing to get started. Mediocrity does not want to be.