The correct answer is: A technical manual explaining how to operate a toaster.
Here we use the definition of "frozen" related to the lack of emotions, affection or warmth. A technical manual gives direct and clear instructions to do something, in this case how to operate a toaster. Therefore no emotions are needed as it is not trying to persuade anyone or make a point. Technical manuals try to give those instructions in the simpler way they can, this to avoid confusion or ambiguity.
In the other options the speaker has a direct contact with an audience, he needs to show a connection between them by using some kind of emotion.
