Read the followingpassage and mark the letter A, B, C or D on your answer sheet to indicate the correct answer to each of the questions.

Not so many years ago, the word vitamin was known only to a few scientists. Today it is very widely used, and the importance of vitamins in your foods is common knowledge.

Vitamins are life-giving substances found in foods and are needed for the proper growth and general health of the body. The different kinds of vitamins are indicated by letters of the alphabet. At the present time, vitamins A, B1, B2, C, D, E and G are known. A proper diet should contain a collection of foods in which all of these vitamins are present. Vitamins are also prepared and sold in tablet and capsule form.

Each vitamin has its particular work to do in the life-giving process. Vitamin B1, for example, benefits appetite and digestion. It also helps the body grow. Another vitami helps the blood to clot, so that danger of bleeding to death in case of injury is lessened. Still another makes the eyes stronger of seeing at night. Airplane pilots need plenty of this vitamin. Scientists think vitamins may have some effect on keeping the hair from turning gray.

Which of the following can be infered from the passage?