302. Iron content more than 0.3 mg/litre
A. causes discolouration of clothes
B. causes incrustation of water mains
C. makes water pleasant to taste
D. makes water reddish.

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303.  The ensure proper growth of children's teeth, the quantity of flouride used in water mains, is
A. 1 mg/litre
B. 2 mg/litre
C. 3 mg/litre
D. 4 mg/litre

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304.  Sluice valves are fitted in a distribution system
A. along straight length of pipes at suitable intervals
B. at the junctions of the pipes
C. at the branching off points of sub-mains
D. all the above.

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305.  In distribution pipes, drain valves are provided at
A. lower point
B. higher point
C. junction points
D. any where.

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306.  In distribution pipes, air valves are provided at
A. lower points
B. junction points
C. higher points
D. any where.

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307.  For a city developed haphazardly, the layout of distribution pipes preferred to, is
A. ring system
B. radial system
C. grid iron system
D. dead end system.

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308. In a well planned city, the layout of distribution pipes generally adopted, is
A. grid-iron system
B. interlaced system
C. reticulation system
D. all the above.

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