Answer :
This should be a simile because a metaphor would be "i was a cloud that floats on high...". Here, we have "as a" used which is the same as using "like a", which is the description of a simile.
The correct answer is C. Simile
Explanation:
Simile is a literary figure in which two things are compared, by using words such as "like" or "as" that establishes a connection between two elements that would not usually be connected, this figure is used in literature, including poems to make descriptions more vivid, this implies through the use of simile the reader can understand better what the writer refers to, as it makes texts more descriptive. In the case of ""I wandered lonely as a cloud/That floats on high o'er vales and hills" the author of this poem compares himself and the way he wanders and floats to the way cloud do over vales and hills, also, he establishes the similarity between himself and the clouds by using the word "as", this does also create an important descriptive style that makes the reader understand and imagine what the poet wrote. Thus, as the author is comparing himself to the cloud, uses "as" to establish a connection and aims at describing two things by stating their similarities this is an example of a simile.