UPSC Prelims 2020 · GS Paper I
Question 76: Environment and Ecology
Steel slag can be the material for which of the following ?
- 1.Construction of base road
- 2.Improvement of agricultural soil
- 3.Production of cement
Select the correct answer using the code given below :
AnswerUPSC’s answer is (d).
Steel slag is a by-product of steelmaking. It is hard and durable, so it is used as aggregate in the base of roads. Its lime and magnesium content lets it work as a soil conditioner that corrects acidity in agricultural soil. Ground slag is also used in cement making. All three uses apply.
- 1. Hard, durable slag is used as road base aggregate.
- 2. Slag is a soil conditioner that corrects acidity.
- 3. Slag is used in cement production.
How you could have got this
- If you were sure statement 1 is correct, (b) goes: it leaves 1 out.
What you needed to know: Hard, durable slag is used as road base aggregate.
- Then, if you were sure statement 2 is correct, (c) goes: it leaves 2 out.
What you needed to know: Slag is a soil conditioner that corrects acidity.
- Then, if you were sure statement 3 is correct, (a) goes: it leaves 3 out.
What you needed to know: Slag is used in cement production.
Only (d) is left. This one needs every statement.
Which options go is worked out from UPSC’s key and the options, not by a model.
Why each option is right or wrong
- (a) Wrong: slag is also used in cement.
- (b) Wrong: slag is also used as road base.
- (c) Wrong: slag is also used to improve soil.
- (d) Right: all three uses apply.
Answer: UPSC’s key. Explanation: written by UPSC Grade, not by UPSC.
Source: UPSC, Civil Services (Preliminary) Examination 2020, General Studies Paper I, Series A. The paper on upsc.gov.in.