821. Venus has the longest day among the listed planets.
822. The shortest (smallest) bone in the human body is stapes.
823. A speedometer is used for measuring velocity.
824. The sub-class of neutron star known for its extremely high magnetic field is a magnetar.
825. The Big Dipper is part of the Ursa Major constellation.
826. The SI base unit for mass is kilogram.
827. Covalent network crystals have a higher melting point than molecular crystals.
828. A substance that increases the efficiency of a catalyst is termed as a promoter.
829. The distance of longitude represents a 4-minute difference in time.
830. A canyon is a large form of a gorge.
831. Rubber tree production is better adapted to areas where the climate is warm and humid.
832. Galvanized Iron sheets have a coating of zinc.
833. Copper occurs in free state.
834. The central part of the Earth is called the core.
835. On passing through food stuff, X-rays can kill bacteria.
836. A man can survive without food for at least 1 month.
837. When the Earth is closest to the Sun, it is called perihelion.
838. Water vapor is a gas.
839. Fog that most often forms as warm rain falls into a cold layer of surface air is called evaporative (mixing) fog.
840. Tesla is the unit of magnetic field strength.