Read the followingpassage and mark the letter A, B, C or D on your answer sheet to indicate the correct word or phrase that best fits each of the numbered blanks.

Agriculture is the world’s most important industry. It provides us with almost all our food. It also (21)_____ materials for two other basic human needs – clothing and shelter. (22)_____, agriculture provides materials used in many industrial products, such as paints and medicines. About half of the world’s workers are employed in agriculture – far more than in (23)_____ industry.

Agriculture is one of the world’s oldest industries. It began about 10, 000 years ago in the Middle East. By that time, certain Middle Eastern tribes had discovered how to grow plants from seeds and how to raise animals in captivity. Having mastered these skills, they could begin to practise agriculture. As agriculture developed and farm (24)_____ increased, fewer people were needed to produce food. The non farmers could then develop arts, crafts, trades and other activities of civilized life. Agriculture therefore not only greatly (25)_____ the food supply but also made civilization possible.

What can be used to replaced “be aware” in the second paragraph?