已知光的速度为300 000 000米/秒，太阳光到达地球的时间大约是500秒，试求出太阳与地球之间的距离大约是多少千米．（用科学记数法表示）

    My grandpa has a farm. The farm is very big and beautiful. There are many animals on the farm. There are ten horses, seven goats, nine cows and many hens. The cows are black and white. The goats are white. The hens are very fat. My grandpa likes vegetables. So  there are a lot of potatoes, green beans, carrots and tomatoes. I like potatoes. My sister likes green beans. We all like this farm very much.

如图所示，用弹簧K₁和K₂的一端拴住滑块M，另一端连在竖直墙壁上，弹簧恰好处于自然状态，滑块静止在O点处．今将滑块M向右推一段后放手，滑块在光滑水平面上来回运动的过程中．由O点向右运动时(    )

Our English ______ far better in a month if we try harder.