Questions

China flicked the switch on the world’s largest floating solar energy plant.  The massive waterborne plant is expected to generate 40 megawatts at one time and could supply electricity for over 15,000 homes. The pioneering project, located in eastern China, is thought to cement China’s status as a top producer of solar energy in the world.  The plant has been built in Huainan city, Anhui Province, by Sungrow Power Supply, a Chinese company specialised in renewable energy.

Relegate means Assigning an inferior rank or position to. That means, downgrading or pulling down, lower a person.

All other options have words with opposite in meaning.

Hence, Relegate is an English word which is similar in meaning to Downgrade.

Sodium hydroxide - NaOH is caustic soda

Sodium carbonate - Na2CO3 is washing soda

Sodium bicarbonate - NaHCO3  is baking soda 

Venus is the only planet that rotates in clockwise where all other planets in the solar system rotates in anti - clockwise direction.

Pluto dwells on the inner edge of the The Kuiper belt which is a belt of asteroids that lies on the outer edge of the solar system.

Pluto is a dwarf planet that is supposed to be no longer a planet and is still considered a planet because of its history in the solar system.

It takes 248 years to make one orbit around the sun. As to where it is, depends on time.