Answer:
The research revealed that cats, on average, sleep 50% more in a 24-hour period than dogs.
Step-by-step explanation:
This sentence uses objective tone because it presents a fact without expressing any personal opinions or emotions. It also uses formal language, as it is written in a scientific or academic style and uses terms such as "research" and "on average." The other sentences express personal beliefs and opinions, and use less formal language, so they are not written in an objective tone or with formal language.