I'm pretty sure it's context, because it's the answer that makes the most sense.
A because if you take out the "who's" turn it into "who is" then does it sound right
It is a simile. A simile is comparing two things with like or as. Example: "They were as quiet as a mouse". Now never confuse this with a metaphor which doesn't use like or as, but still compares two things. Example: "She is a walking encyclopedia" . This is telling you indirectly that she is a very smart and talkative person. A simile would tell you directly
Answer:
The car mechanic working too quickly, had forgotton to reattach the oil filter.
Explanation:
