31 29 23 () 17 13 11
A.21
B.20
C.19
D.18
31 29 23 () 17 13 11 A.21 B. 20 C. 19 D. 18
11,13,17,19,23,() A.27 B.29 C.31 D.33
11, 13, 17, 19, ()。 A.21B.23C.27D.29
31,29,23,(),17,13,11。 A.21B.20C.19D.18
31,29,23,(),17,13,11A.21B.20C.19D.18
31,29,23,(),17,13,11 A.21 B.20 C.19 D.18