Which is correct?(2)

[Shinya Maki]

Hello, everyone.

Are both of the two, #1 and #2, possible in the blank below? Or is only #1 correct?

We ( ) the other road. If we had, we might have arrived earlier.
1. should have taken
2. must have taken

Any comment would be appreciated.
Thanks in advance.

Best regards,
Shinya Maki

[DeNayGo]

Only #1 is correct.

When I say "It must have happened", I don't know whether it happened, but am absolutely sure it did, which, in the sentence above, doesn't make any sense.

When I say "It should have happened", I know it didn't happen, but think it would've been good if it had happened.