: during the program running, the values of each variable are as follows: a1=1 n=2? Continue the loop?

before cycling? a2=a1+1=2? 3/

the first lap? a3=1a2=12? 4 yes?

the second lap? a4=a2+1=3? 5 is?

the third lap? A5 = 1A4 = 136 Yes?

the fourth lap? a6=a3+1=32 7 ? Yes?

the fifth lap? a7=1a6=23 8? It does not loop

, so the final output an value is: 13.

Therefore, it is selected as C. 。