Help Detective Clouseau finish his rather embarrassing report about the museum heist. Choose the correct complex modal phrases to complete his deductions.

"The thieves were entirely too coordinated. They must have been monitoring my daily patrol route for weeks! However, they needn't have hacked the laser grid, because I had accidentally left it turned off anyway. Ultimately, the legendary Ruby of Doom could not have been stolen by them, as I had already sent it to the dry cleaners in my other jacket."

The thieves must have been monitoring my daily patrol route for weeks!

We use must have been + -ing to make a strong logical deduction about an ongoing or repeated action in the past.

However, they needn't have hacked the laser grid...

Needn't have + past participle is used to express that an action was performed in the past, but it was completely unnecessary.

...the legendary Ruby of Doom could not have been stolen by them...

Could not have been + past participle expresses a strong logical impossibility in the past, formatted in the passive voice because the subject is the ruby.