完形填空

  It was very hot in the middle of summer and there were no trees 1the street. Mr. Read 2 his shop at half past five, and went 3 into the street and began walking to the bus stop. He was very 4. The sun shone straight down the street, and in a few minutes Mr. Read5very hot.

     A small boycame out of another6 in the street and 7Mr. Read. He stayed very8 him all the time, and he kicked Mr. Read's 9several times. Mr. Read looked at him 10 each time.

     After thefourth time, Mr. Read stopped, turned 11 and said to the small boy, "What are you doing? 12 following me like that! You're going to 13 my feet."

     "I'm 14, but don't stop me, please!" The small boy said, "It's very hot today, and there isn't 15shade anywhere else in the street."

有一种运动叫蹦极，如图所示是蹦极运动的简化示意图，弹性绳一端固定在O点，另一端系住运动员，运动员从O点自由下落，A点处弹性绳自然伸直。B点是运动员受到的重力与弹性绳对运动员拉力相等的点，C点是蹦极运动员到达的最低点，运动员从O点到C点的运动过程中忽略空气阻力，则（   ）