Final answer:
China is the large country with only one time zone, following Beijing time throughout its entire territory, despite its large geographical span.
Step-by-step explanation:
Among the options provided, the country that is large in terms of area but only has one time zone is China. While other large countries like Russia, Canada, and the United States have multiple time zones due to their vast geographical span, China has chosen to operate under a single time zone for the entire nation, despite its size. This one time zone is known as Beijing time, and it applies across the country, from densely populated coastal areas to the less inhabited western regions, such as Tibet, where the sun may rise at what feels like an unusual time according to the clocks.