In addressing the west wind, Shelley used the literary technique of

O personification

metaphor

apostrophe

The answer is letter C. apostrophe.

Explanation:

Apostrophe can be defined as a figure of speech in which the author or speaker of a poem speaks directly to someone who is absent or dead, or to an inanimate object. Shelley uses this technique in his poem "Ode to the West Wind". The speaker addresses the wind, talks to it, as if the wind could hear and understand his words. He even addresses the wind as "thou":

O wild West Wind, thou breath of Autumn's being,  

Thou, from whose unseen presence the leaves dead  

Are driven, like ghosts from an enchanter fleeing,

[...]

Will take from both a deep, autumnal tone,  

Sweet though in sadness. Be thou, Spirit fierce,  

My spirit! Be thou me, impetuous one!

[..]

about the letter or who wrote the letter