The element used for making solar cells is
1). Magnesium
2). Sodium
3). Calcium
4). Silicon
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1. Aqua regia is a 1:3 mixture by volume of
3. Supersonic Jet causes pollution by thinning of
4. ________ gives hardness to stainless steel.
5. Which of the following is used to iodine common salt
6. _______ is the major component of natural gas.
7. Silver halides are used in photographic plates because they are
9. Which one of the following group of gases contributes to the 'Green House Effect'?
10. Which of the following fuels causes minimum environmental pollution?