4231: Which of the following periods can be considered as the era of mass revolution?
(a) 1856-1885 A.D.
(b) 1757-1857 A.D.
(c) 1920-1947 A.D.
(d) 1901-1919 A.D.
4232: There are 10 identical coins and each one of them has H engraved on its one face and T engraved on its other face. These 10 coins are lying on a table and each one of them has H face as the upper face.
In one attempt, exactly four (neither more nor less) coins can be turned upside down. What is the minimum total number of attempts in which the T faces of all the 10 coins can be brought to be the upper faces ?
4233: Though a few (gas-based) industries have already been established good reserves of natural gas in India remain unutilised. This vast resource of natural gas can be used in the production of
(a) fertilizers
(b) carbide
(c) graphite
(d) synthetic petroleum
4234: Punjab and Haryana receive rainfall from:
(a) Westerly disturbances
(b) Cyclones in Bay of Bengal
(c) Both of the above
(d) None of the above
4235: Mycorrhizal biotechnology has been used in rehabilitating degraded sites because mycorrhiza enables the plants to
1. resist drought and increase absorptive area
2. tolerate extremes of pH
3. resist disease infestation
Select the correct answer using the codes given below.
(a) 1 only
(b) 1 and 3 only
(c) 2 and 3 only
(d) 1, 2 and 3