现阶段我国仍然处在社会主义初级阶段，这是因为[ ]

①生产力水平还比较低

②地区发展不平衡

③科学技术水平还不够高

④社会主义社会的具体制度还不够完善

A．①②③④

B．②③④

C．①②④

D．①③④

Wow! There are so many books. I really can't decide _____. [ ]

A. where to buy

B. which to buy

C. what to buy

D. how to buy