Select the most appropriate option to fill in the blank.
Is this, I have wondered, the growth of a spirit of resignation, or is it a ________ of the texture?

Correct option is B

The correct option to fill in the blank is (b) toughening.
Explanation: The blank follows “a”, so we need a noun/gerund phrase that can name a process: “a toughening of the texture” is grammatically correct and natural in meaning (a process of becoming tougher). Toughening (V-ing) works as a gerund (noun) here. ( कठोर होना/सख़्त होना)
Example: Regular kneading causes toughening of the dough.
Explain why other options are incorrect:
· (a) toughen: base verb; would need “to” or a helping verb (e.g., “will toughen”), not “a ___ of” ( सख़्त करना/होना)
· (c) tough: adjective; “a tough of the texture” is grammatically wrong ( सख़्त)
· (d) toughened: past participle/adjective; “a toughened of the texture” is incorrect; you could say “a toughened texture,” but not “a toughened of…” ( सख़्त हुआ)