Multiple choice

Directions: The following items consist of two statements, one labelled as 'Assertion (A)' and the other labelled as 'Reason (R)'. You are to examine these two statements carefully and decide if the Assertion (A) and the Reason (R) are individually true and if so, whether the reason is a correct explanation of the Assertion. Select your answer to these items using the codes given below. Assertion (A) : Basalt is a fine-grained and dark coloured igneous rock which is formed below the earth's surface. Reason (R) : The rate of cooling and solidification of magma inside the earth is very slow.

  1. Both A and R are true and R is the correct explanation of A.

  2. Both A and R are correct but R is not the correct explanation of A.

  3. A is true but R is false.

  4. A is false but R is true.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Both statements are individually true but the reason is NOT the correct explanation. Basalt is indeed fine-grained and dark-colored, and slow cooling produces coarse-grained rocks like granite, not fine-grained basalt. Basalt forms from RAPID cooling of magma at or near Earth's surface (extrusive or shallow intrusive). The slow cooling described in R would produce coarse-grained texture, not the fine texture of basalt.

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