—What about the student in your class, Mr. Wang?

—The doctor said that ________ sleep caused him poor memory and poor concentration.[ ]

A. lacking of  

B. lacked in    

C. lacking    

D. lack for

气管和支气管中对“痰”的排出起主要作用的是[ ]

A．平滑肌

B．腺细胞

C．纤毛

D．毛细血管