Answer:
C: slowly and deliberately in secret
Explanation:
Stealthily is an adverb used to describe that something is done secretly and quietly in order not to be seen or heard, so that people do not realize what is happening.
Spiware stealthily installs itself on computers.
Answer:
B: Persistence
Explanation:
The noun doggedness describes a person who is very determined to continue doing something, even if it is very difficult.
His doggeness helped him to succeed.
