WHICH OF THE FOLLOWING WAS NOT MENTIONED IN THE PASSAGE AS A SOUR...

30. Which of the following was NOT mentioned in the passage as a source of information for The Sea Around Us? A. printed matter B. talks with experts C. a research expedition D. letters from scientists Read the following passage and then choose one best answer A, B, C, or D Experiments have proved that children can be instructed in swimming at a very early age. At a special swimming pool in Los Angeles, children become expert at holding their __(31)__ under water even before they can walk. Babies of two months old do not appear to be reluctant to enter the water. It is not long before they are so accustomed to swimming __(32)__ they can pick up weights from the floor of the pool. A game that is very popular __(33)__ these young swimmers is the underwater tricycle race. Tricycles are lined up on the floor of the pool seven feet under water. The children compete against each other to reach the __(34)__ end of the pool. Many pedal their tricycles, but most of them prefer to push or drag them. Some children can cover the whole length of the pool without coming up for breath even once. Whether they will ever become future Olympic __(35)__, only time will tell. Meanwhile, they should encourage those among us who cannot swim five yards before they are gasping for air.