—Susan is Bob's best friend,  isn't she?            

—Yes, she often       _  when he is in trouble.           [ ]

A. helps Bob out             

B. takes Bob after          

C. puts up Bob                    

D. sets up Bob

细胞性水肿是由于________所致，引起双极细胞、神经节细胞及神经纤维层水肿、混浊；细胞外水肿是由于________受损，引起视网膜水肿。