Answer:
The adverb that applies is option A) Stealthily
Step-by-step explanation:
Stealthily means in a silent and unassuming manner to avoid being caught.
This adverb clearly explains the situation and reason for the clerk's resignation in the face of an overwhelmingly difficult database conversion project.
Leaving silently in a surreptitious manner would be considered more effective as more hands would be needed on deck and the possibility of granting leave would be very slim.
The clerk probably found a very good excuse that could not be refused,