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Following are the different steps carried out in a waste water treatment plant. These steps are arranged in a random fashion. Select the option that arranges these steps in the correct sequence.
(i) Wastewater is passed into sedimentation tank.
(ii) Sludge is decomposed by anaerobic bacteria.
(iii) Wastewater is passed through bar screens.
(iv) Wastewater is passed to grit and sand removal tank.
(v) Solids settle at the bottom and floatable materials are removed by skimmer.
(vi) Aeration of water takes place.
(vii) Disinfection of water by adding chlorine.

A(iii) → (i) → (iv) → (v) → (ii) → (vi) → (vii)
B(iii) → (iv) → (i) → (v) → (ii) → (vi) → (vii)
C(iv) → (vi) → (v) → (iii) → (ii) → (i) → (vii)
D(iv) → (v) → (vii) → (ii) → (vi) → (i) → (iii)

The given statements correspond to which of the following layers of forest?
(i) It is the thickest layer and much of the sunlight and rain is stopped by the thick foliage.
(ii) The trees may be as high as 100 feet.
(iii) The animals found in this layer include birds, monkeys, sloths, lizards, etc.

AEmergent layer
BUnderstorey
CCanopy
DForest floor

Three solutions of different substances P, Q and R gave the following results with different indicators.
Solution P : Turns methyl orange red.
Solution Q : Turns turmeric solution red.
Solution R : Turns phenolphthalein solution pink.
Identify the solutions P, Q and R respectively

AAntacid, soap solution, lemon juice
BBaking soda, shampoo, antacid
CLemon juice, sodium hydroxide, baking soda
DVinegar solution, antacid, lemon juice.

Observe the given experimental setup carefully.

Which of the following statements is/are correct?
1. The nails in flask I will rust because both water and oxygen are available.
2. Nails in flask II will not rust because tap water contains impurities.
3. Nails in flask III will not rust because both oxygen and water are not available.

A2 only
B1 and 3 only
C3 only
DNone of these

Identify W, X and Y in the given figure and select the correct option regarding them.


AY is the chamber where partially chewed food is stored temporarily.
BW is the chamber which is often referred to as true stomach which leads to small intestine.
CX is the chamber where anaerobic bacteria helps in the digestion of cellulose.
DX is the chamber where protein is digested with the help of enzymes.

Soil erosion can be prevented by

AAfforestation
BDeforestation
COvergrazing by animals
DBoth A and B.

Study the given list of source of water.
(i) Sea
(ii) Well
(iii) Stream
(iv) River
(v) Hand pump
(vi) Tube well
(vii) Ocean
(viii) Pond
(ix) Lake
Which of the following options correctly identifies the numbers of source of surface water (X) and source of ground water (Y)?

Which of the following statements is false?

AMeasuring tape is not suitable to measure the girth of a tree.
BA suitable measuring device is must to measure the length of an object.
CIn ancient India, small length measurements used were an angul or a mutthi.
DElectric trains, monorail, supersonic aeroplanes and spacecrafts are some of the 20^th century contributions.

A point source of light S, placed at a distance 1 m in front of the centre of a plane mirror of width 2 m, hangs vertically on a wall. Rahul walks in front of the mirror along a line parallel to the mirror at a distance 2 m from it as shown in the figure. The greatest distance over which he can see the image of the light source in the mirror is


A5 m
B9 m
C12 m
D6 m

Refer to the given Venn diagram. Which letter in it best represents "nitrogen gas"?


AP
BQ
CR
DS