SOLVED PAPER 2021 (CDS) (II) (General Studies)

Total Questions: 120

111. What is the name of the process that converts sulphide ores into oxides by heating strongly in the presence of excess air?

Correct Answer: (b) Roasting·
Solution:Roasting is a process of heating a sulfide ore to a high temperature in the presence of air. It is a step in the processing of certain deres. This process is generally applied to sulfide minerals. During roasting, the sulfide is converted to an oxide and sulfur is released as sulfur dioxide, a gas.

112. What are the constituents of alloy solder?

Correct Answer: (b) Pb and Sn
Solution:The composition of solder alloy is 50 per cent lead (Pb) and 50 per cent tin (Sn).It has a very low melting point that is quite less than its constituting metals (Pb and Sn). Thus, solder is widely used in soldering and welding of electrical wires.

113. Which of the following limits the number of trophic levels in a food chain ?

Correct Answer: (c) Decrease in the available energy at higher trophic levels
Solution:Energy in the form of food decreases as it moves up trophic levels in food chain because 90% energy is lost as metabolic heat on each trophic level as organisms from one trophic level are consumed by organisms from the next level. Trophic Level Transfer Efficiency (TLTE) measures the amount of energy that is transferred between trophic levels. Thus, decrease in the available energy at higher trophic levels limits the number of trophic levels in a food chain available.

114. In pea, a pure tall plant (TT) is crossed with a short plant (tt). What will be the ratio of pure tall plants to short plants in the F2 generation?

Correct Answer: (a) 1 : 1
Solution:The ratio of pure tall plants to pure short plants in F₂ generation will be 1 : 1 because according to the mechanism of inheritance, when a pure homozygous tall plant and short plant crossed together, the resulting off springs of F₁ generation are all tall. In the F₂ generation, the tall and dwarf plants will be produced in 3 : 1 ratio. Out of the three tall plants, one tall plant will be homozygous tall (TT) and two tall plants will be heterozygous tall (Tt).

115. Which one of the following statements about variations is not true?

Correct Answer: (b) All variations in a species have equal chances of survival.
Solution:All variations in a species will not have equal chance of survival as according to ‘Survival of the fittest’, only the species with adaptable variation which can adapt themselves to the environment can survive. Selection of the variants occurs by the different environmental factors harmful. Variations that are not suitable or advantageous to the organism in the prevailing environmental conditions are not maintained.

116. While studying vegetation of an area, terms like ‘population’ and 'community' are often used. Which one of the following statements best describes a population ?

Correct Answer: (d) A group of organisms of more than one species, living in the same area at the same time.
Solution:A population refers to a group of organisms of a species that interbreed and live in the same place at the same time. It is a group of one particular species in a particular place. with interacts of species level. Community is a group of all organism or species found in a particular area which interact with one-another through interspecific interactions. Community are named after local dominant vegetation type e.g. grassland community, forest community etc.

117. In the human body, blood flows through a process of double circulation. Which one of the following statements is true in this regard?

Correct Answer: (a) Oxygenated blood reaches the left side of the heart from the lungs.
Solution:Double circulation is a process by which blood passes twice through the heart during one complete cycle. It is oxygenated in the lungs and comes back to the heart. From left side of heart oxygenated blood is distributed to all parts of the body. Hearts’s right side collect deoxygenated blood and send it to lungs for oxygenation.

118. In which of the following groups of organisms, is food material broken down outside the body and absorbed ?

Correct Answer: (a) Yeast, mushroom, bread mould
Solution:Organism like Mushroom, Yeast and Bread mould are saprophytic fungi They break down dead organic compounds outside the body and absorb the simpler digested nutrients particles. This is known as extracellular digestion.

119. A sound wave has a frequency of 4 kHz and wavelength 30 cm. How long will it take to travel 2.4 km?

Correct Answer: (a) 2.0 s
Solution:

120. An electric bulb is connected to a 110 V generator. The current is 0.2 A. What is the power of the bulb?

Correct Answer: (c) 22 W
Solution:C. Power = Voltage × Current
Voltage = 110 V
Current = 0.2 A
Thus, power = 110 × 0.2 = 22 watt