Answer: Our old toaster always burns the toast on one side.
Step-by-step explanation:
In active voice, we place focus on the agent that performs the action. The last sentence - Our old toaster always burns the toast on one side, is thus the only sentence in the active voice. 'Burns' is a present simple tense from the verb 'to burn'.
All the other sentences are written in passive voice, as the focus is put on the object/person that receives the action. Passive voice construction consists of verb to be and past participle (as in was negotiated, was colonized, and was quoted).