n 5 ( 6 " (2017 2018 c 1 ) : 6: : K n o o !JJJKKK zzzKKK2, 30 1. a.n|O ( ) (A) 'X (B) !6( (C) !a. (D) (a. 2. k: LChead, K^ ( ) (A) headNULL (B) head-nextNULL (C) head-nexthead (D) head!NULL 3. A: ( )