(a)  reduces evaporation of petrol
     (b)  increases efficiency of petrol
     (c)  prevents freezing of petrol
     (d)  reduces consumption of petrol
Ans: (c)
289. What is the main constituent of a Pearl? [CDS 2011]
     (a) Calcium carbonate and magnesium corbonate
     (b) Calcium sulphate only
     (c) Calcium oxide and calcium sulphate
     (d) Calcium carbonate only
Ans: (a)
290. From which one among the following water sources, the water is likely to be contaminated with fluoride? [CDS 2011]
     (a) Groundwater
     (b) River water
     (c) Pond water
     (d) Rain water
Ans: (a)
291. Which one among the following will you put into pure water in order to pass electric current through it? [CDS 2011]
     (a) Kerosene
     (b) Mustard oil
     (c) Lemon Juice
     (d) Sugar
Ans: (c)
292. Math the following: [CDS 2011]
     Acid                    Source
     A. Lactic acid          1. Tamarind
     B. Tartaric acid        2. Orange
     C. Oxalic acid          3. Tomato
     D. Citric acid          4. Sour curd
          A         B        C           D
     (a)  2         3        1           4
     (b)  2         1        3           4
     (c)  4         3        1           2
     (d)  4         1        3           2
Ans: (d)
293. Cutting and peeling of onions brings tears to the eyes because of the presence of [CDS 2011]
     (a) sulfur in the cell
     (b) carbon in the cell
     (c) fat in the cell
     (d) aminoacid in the cell
Ans: (a)