---What did the boy do just now?---He ran the road to pick up his ball.A across B through

问题补充：

---What did the boy do just now?

---He ran the road to pick up his ball.

A across B through C by D for

答案：

解析：本题考查介词。句中across表示“穿越”之意。句意：——那个男孩刚才做什么？——他穿越马路去捡他的球。