Practice Test 24: The Story of the Bicycle and Farming in the City

A The bicycle looks like a simple machine, yet it took most of the nineteenth century to arrive at its modern form. The earliest ancestor, built by the German inventor Karl von Drais in 1817, had two wheels and a steering handle but no pedals. Riders pushed themselves along with their feet, and the machine was known as a running machine. It was a fashionable novelty for a few years but was soon overtaken by other fads.

B The next step was to add pedals. In the 1860s French makers attached cranks directly to the front wheel, which made travel faster and smoother than pushing with the feet. Because one turn of the pedals moved the bicycle forward by one turn of the wheel, makers increased the size of the front wheel to go faster. This led to the high wheeler, with a front wheel as tall as a man, which was fast but dangerous: riders sat high above the ground and could be thrown forwards over the handlebars.

C The solution came in the 1880s with the safety bicycle. It had two wheels of equal size and a chain that carried power from the pedals to the rear wheel, so the rider could sit low and the gearing could be adjusted without enlarging a wheel. A few years later the invention of the pneumatic tyre, filled with air rather than made of solid rubber, absorbed the shocks of rough roads and made cycling far more comfortable.

D These changes widened the bicycle's appeal. Early machines had been used mainly by young men with money to spare, but the safety bicycle was cheaper and easier to ride, and many women and working people took it up. Historians have argued that cycling gave women new independence of movement, and that the demand for good roads, created by cyclists, later helped the motor car.

A As the world's cities grow, interest is rising in growing food inside them. Urban farms range from small gardens on roofs and vacant plots to large indoor facilities where crops are stacked in layers under artificial light. Supporters argue that producing food close to where it is eaten cuts transport, reduces waste in transit and gives residents fresh produce.

B Many indoor farms use hydroponics, in which plants grow in nutrient rich water rather than soil. Because the water is recycled, these systems can use far less of it than field farming, and because conditions are controlled, crops can be grown all year and without pesticides. Leafy vegetables and herbs, which grow quickly and weigh little, are the most common crops.

C However, the approach has limits. Artificial lighting and climate control use a great deal of electricity, which can make indoor produce expensive unless cheap, clean power is available. Staple crops such as wheat and rice need much more space and light than a city can provide, so urban farms are unlikely to feed a city on their own.

D Many experts therefore see urban agriculture as a complement to conventional farming, not a replacement. Its value may lie as much in education and community as in tonnes of food: gardens in schools and neighbourhoods can teach children where food comes from and bring neighbours together. Where land is scarce and food travels far, it can also add resilience to supply.