A number arrangement machine arranges numbers step by step in particular order according to a set of rules. The device stops when the final result is obtained.

Input: 6 12 3 9 11 7 8

Step I:3 6 12 9 11 7 8

Step II:3 6 7 12 9 11 8

Step III:3 6 7 8 12 9 11

Step IV :3 6 7 8 9 12 11

Step IV: 3 6 7 8 9 11 12

Study the above arrangement carefully and then answer the following question:

Which of the following will be the third step of input below:

Input:12 17 15 19 34 21 16