Complete the frantic email from a science student explaining why the laboratory is currently covered in purple foam. Choose the correct verb phrases for each blank.

"Dear Professor, to start with, the beaker of unstable chemicals ought to have been left in the cooling chamber, but someone placed it on the radiator instead. I admit I might well have been daydreaming when the mixture started bubbling, because I completely missed the warning signs. Still, the resulting explosion can't have been triggered solely by my mistake; I strongly suspect the baking soda was actually gunpowder!"

...the beaker of unstable chemicals ought to have been left in the cooling chamber...

Ought to have been + past participle is a past passive modal expressing a criticism or an unfulfilled obligation (the right thing to do was to leave it there, but it wasn't done).

I admit I might well have been daydreaming...

Might well have been + -ing expresses a strong possibility that a continuous action was happening in the past. Adding "well" emphasizes the likelihood.

...the resulting explosion can't have been triggered solely by my mistake...

Can't have been + past participle is a passive deduction expressing that something was logically impossible in the past.