IT IS IMPORTANT THAT HE ______ A GALLON OF WATER WITH HIM IF HE WANTS TO HIKE TO THEBOTTOM OF THE GRAND CANYON

Questions 44: It is important that he ______ a gallon of water with him if he wants to hike to the

bottom of the Grand Canyon.

A. taking B. takes C. took D. take

Read the following passage and mark the letter A, B, C or D on your answer sheet to indicate the

correct answer to each of the questions.

Water scarcity is fast becoming one of the major limiting factors in world crop production. In many

areas, poor agricultural practices have led to increasing desertification and the loss of formerly arable

lands. Consequently, those plant species that are well adapted to survival in dry climates are being

looked at for an answer in developing more efficient crops to grow on marginally arable lands.

Plants use several mechanisms to ensure their survival in desert environments. Some involve purely

mechanical and physical adaptations, such as the shape of the plant's surface, smaller leaf size, and

extensive root systems. Some of the adaptations are related to chemical mechanisms. Many plants,

such as cacti, have internal gums and mucilage which give them water-retaining properties. Another

chemical mechanism is that of the epicuticular wax layer. This wax layer acts as an impervious cover

to protect the plant. It prevents excessive loss of internal moisture. It also protects the plant from

external aggression, which can come from inorganic agents such as gases, or organic agents which

include bacteria and plant pests.

Researchers have proposed that synthetic waxes with similar protective abilities could be prepared

based on knowledge of desert plants. If successfully developed, such a compound could be used to

greatly increase a plant's ability to maintain health in such adverse situations as inadequate water

supply, limited fertilizer availability, attack by pests, and poor storage after harvesting.