There was a thunder on the ground
平地───flat ground;一声雷───A thunder
Uphill running forces you to drive your arms harder than you do when running on flat ground, so you'll improve your upper body strength.───您的上身有劲：跑坡道迫使您摆臂比跑平地时更加用力，因此，您的上身力量可以提高。
is, of course, assuming they don't suffocate, say, if you dropped them from 40,000 feet, and that they land on relatively flat ground (nothing pointy or the like).───当然，前提是它们不会因窒息而死，(如果你从40000英尺让猫们掉下来它们会因缺氧被憋死)另外一个前提是：它们着陆的地面要相对平坦。
If you run or bike or walk for cardio, you'll want to incorporate hills (after the first month or two of doing it at an easy pace on flat ground).───如果你通过跑步，骑车或者走路来锻炼心脏，那么结合斜坡，效果更好(通常在平地上锻炼一两个月以后进行。)
The moon was shining brightly on the great stones, and between them, on the flat ground, lay the girl.───月光明朗地照两根大石柱上，而那位少女就躺在它们之间的平地上。
Turning round the hillside, we found a tract of flat ground. At its end, we saw a house shrouded in the dim light of night.───转过山腰，有一片平地，夜色朦胧中看见平地的尽头有一所屋宇，我们齐说，好了，找到一户人家了。
Uphill running forces you to drive your arms harder than you do when running on flat ground, so you'll improve your upper body strength.───使您的上身有劲：跑坡道迫使您摆臂比跑平地时更加用力，因此，您的上身力量可以提高。
Flat ground and the slopes of the Marne valley are particularly prone to frost.
Dazed, we wandered along flat ground towards the lake, when we heard the roar of an approaching speedboat.
In the middle of the flat ground stood two great stones.
They leveled the hillock to flat ground and began to grow crops.
In the shallow sea area of circum- Buohai bay with shallow sea water, flat ground under water, thick sludge and wide intertidal zone, the estimated petroleum reserves is 200 million tons.