Mountain climbing must be very tiring, ________,you might feel sick with the air getting thinner. 

A．In addition

B．In turn

C．In return

D．In case

—Do you think Mark Twain's stories are ______?  

—Yeah. Most of us are ______ in his stories.[ ]

A. interesting, interested    

B. interested, interesting

C. interesting, interesting  

D. interested, interesting