那男孩用石子掷击小流氓的背脊.The boy gave the bully a pelt on the back with a pebble.男孩子喜欢在湖面上用石子打水漂.The boys liked to skip stones on the lake.他们也许是用石子来作计算的, 因“calculus ” 这个字原意是 “ 石子 ”.They may have used pebbles to calculate, for the ...