Double-decker buses are still extant in some cities of India.

Answer: Option C

Extant : still in existence; surviving.
Unheeded : heard or noticed but disregarded.
Forgotten : unremembered.
Destroyed : end the existence of (something) by damaging or attacking it.
Extinguished : cause (a fire or light) to cease to burn or shine.

Antonym of Extant is Destroyed