21000+ Important MCQs for UPSC

21) The segment of a myofibril that is called a sarcomere runs from

22) The ultra violet radiations of the Sun do not reach the Earth because the upper layers of the atmosphere contain

23) Consider the following statements about HPLC:
1.it stands for high performance liquid chromatography.
2.it is used to separate isomeric compounds.
3.its operations involve a solid and a liquid phase. 
The correct statement(s) is/are:

24) In the structure of planet Earth below the mantle, the core is mainly made up of

25) The human fossils living 100,000 to 30,000 years ago, in Europe, Asia and parts of Africa, with short stature, heavy brows, retreating fore heads, large jaws with heavy teeth, stocky bodies, a lumbering gait and stooped posture were

26) Consider the following chemicals:
1.Benzene
2.Carbon tetrachloride
3.Sodium carbonate
4.Trichloroethylene The chemicals used as dry cleaning agent(s) is/are

27) Roxarsone, an arsenic containing nitrophenol is used as

28) Bakelite is
1.Obtained from phenol and formaldehyde
2.Obtained from phenol and formic acid
3.Used as a plastic
4.Obtained from adipic acid and caprolactam The correct answers are:

29) When iron and wood are exposed to sunlight, the iron rod becomes hot quickly because of

30) Aluminium is extracted from bauxite