Answer: It has a negative connotation
Step-by-step explanation: A simile makes a comparison using the words “like” or “as.” Example: The concert was so crowded, it felt like a million people were there. A metaphor makes the comparison directly, substituting one thing for another. Example: That test was a killer.
In this case "The mosquitoes buzzed in the air around my hair like a swarm of miniature assassins." is a simile so the answer above is not correct.
Negative connotation is the bad feeling or emotion that is connected to a word.
Positive connotation is the good feeling or emotion that is connected to a word.
In the sentence "The mosquitoes buzzed in the air around my hair like a swarm of miniature assassins." They are angry at the mosquitoes therefore they have a bad feeling in this sentence hence why this has a negative connotation.