Correct answer: (b) The social classification of Varna was known to Sangam poets.
Explanation
- A
Sangam poems are devoid of any reference to material culture.
No material culture. Sangam is full of pots, cloth, ports and ploughs.
- B
The social classification of Varna was known to Sangam poets.
Varna was known to Sangam poets. The keyed statement.
- C
Sangam poems have no reference to warrior ethic.
No warrior ethic. Puram poetry is war and honour.
- D
Sangam literature refers to magical forces as irrational.
Magical forces as irrational. Sangam does not dismiss the sacred that way.
Summary. Official key is (b). Sangam poems know a fourfold social classification akin to varna, even as tinai and clan matter more on the ground. They are rich in material life and warrior ethic, and they do not treat the sacred as mere irrational magic.