**The ozone layer is present about 30 miles (50 km) in the atmosphere above Earth. The stratum (layer) of atmosphere in which the ozone layer lies is:**A) ExosphereB) MesosphereC) StratosphereD) Ionosphere Show Answer Correct Answer: C – Stratosphere
**Which rocks are formed by the alteration of pre-existing rocks by great heat or pressure:**A) Igneous rocksB) Sedimentary rocksC) Metamorphic rocksD) Acid rocks Show Answer Correct Answer: C – Metamorphic rocks
**The most abundant natural iron oxides are:**A) Magnetite and PyriteB) Magnetite and BauxiteC) Hematite and PyriteD) Hematite and Magnetite Show Answer Correct Answer: D – Hematite and Magnetite
**The most abundant elements in seawater are:**A) Sodium and PotassiumB) Sodium and CalciumC) Sodium and ChlorineD) Chlorine and Iodine Show Answer Correct Answer: C – Sodium and Chlorine
**An electric current can produce:**A) Chemical effectB) Magnetic effectC) Heating effectD) All of these Show Answer Correct Answer: D – All of these
**The unit of home electricity energy consumption is:**A) Watt hourB) Kilowatt hourC) Joule hourD) Kilojoule hour Show Answer Correct Answer: B – Kilowatt hour
**A magnet always points in the same direction, if it moves freely, i.e., towards north and south poles, because of:**A) Gravitational fieldB) A lot of metal deposits on north and south polesC) Due to attraction of north pole and repulsion of western poleD) Earth is a huge magnet Show Answer Correct Answer: D – Earth…
**When sound is reflected from floor, ceiling, or a wall, it mixes with the original sound and changes its complexion, it is called:**A) SoundB) EchoC) ReverberationD) Noise Show Answer Correct Answer: C – Reverberation
**The speed of sound in dry air at 20°C is about:**A) 130 meters per secondB) 230 meters per secondC) 330 meters per secondD) 550 meters per second Show Answer Correct Answer: C – 330 meters per second
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