Chọn một từ thích hợp trong ô dưới đây điền vào mỗi chỗ trống để hoàn thành đoạn văn sau.

If you live in a city, you will probably see many people; hear the noise of traffic and smell the ..... from cars and factories. We are living in a new era in the history of the world. Before this, most people were farmers. They lived in small communities ..... the country. Now many people are leaving the farms and moving into the cities. They are looking for ..... job. As a result, the cities are growing quickly. Most cities are becoming more crowded. People are driving more cars, burning more fuel, using more water, eating more foods, ..... more garbage, and producing more things in factories than ever before. Life in modern cities can ..... many opportunities, but also many difficulties.