Yesterday our teacher _____a singer to our class. [ ]

A. invite  

B. to invite

C. invited    

D. has invited

近代中国，民族资本主义在外国资本主义和封建主义的夹缝中顽强生存，其发展特点是[ ]

A．严重倒退

B．顺利发展

C．停滞不前

D．曲折发展