You had it right, it is a simile because it uses the word as.
The essential appositive in the sentence "astronomer maia mitchell discovered a comet in 1847 and went on to become the first professional female astronomer in the united states," is Maia Mitchel. The last option is correct.
An appositive consists on a noun or noun phrase that renames another noun right beside it. The appositive can be a short or long combination of words.
In this particular case, the words Maia Mitchell which is a proper noun is renaming the noun astronomer, which is right before it and constitutes the subject of the sentence.
સારું પ્રથમ તમારે મારી ભાષા મૂંગું મૂર્ખ સમજવું જોઈએ
Can you give me a sentence or something that shows them interacting?
