10, the period of the earth's revolution speed gradually slowing down is a.① ~ 2b. ② ~ 3c。 ③ ~ 4d。 ④ ~ 1o。

Analyze this small problem and investigate the change of the revolution speed of the earth. The sun is located in a focal point of the earth's orbit around the sun, and the distance between the sun and the earth is constantly changing. The closest point to the sun is called perihelion, with the time of 65438+1early October, and the fastest revolution speed; The point farthest from the sun is called apohelion. At the beginning of July, the revolution speed is the slowest. According to the picture, ① is the summer of solstice, about June 22nd. It's the autumnal equinox, around September 23rd. ③ Winter solstice, around 65438+February 22nd. ④ It is the vernal equinox, about 2 1 on March. A, ① ~ ② The speed is slow first and then fast. So, A is wrong. B, ② ~ ③ The rotating speed becomes faster. So, B is wrong. C, ③ ~ ④ The rotating speed first becomes faster and then slows down. So, C is wrong. D, ④ ~ ① The rotation speed slows down. Therefore, d is correct. Answer d