---Why are you so late?

---I was on the way when it       to me that I had left my book home,so I had to fetch it.[ ]

A. occurred        

B. hit          

C. happened      

D. reminded

初中生在解决问题时已出现抽象思维，这种现象在皮亚杰的思维发展阶段理论中属于哪一阶段？（）

A.感知运动阶段

B.前运算阶段

C.具体运算阶段

D.形式运算阶段