it is the one with the most keychains.
As this graph shows the evolution of your collection over time, and not the number of key chains you collected in each month, you need to look for the month with the highest increase.
According to the graph on the first month you collected 4 key chains. After the 2nd month you had 6 key chains, so, you collected:
keys on 2nd month - keys on 1st month = 6-4 = 2 keys
In month 3 you went from 6 to 10 key chains, so you collected
keys on 3rd month - keys on 2nd month = 10-6 = 4 keys
On the next, month 4, you had 16, so you collected
keys on 4th month - keys on 3rd month = 16-10 = 6 keys
Finally, on the last month you had 18, having collected:
keys on 5th month - keys on 4th month = 18-16 = 2 keys
So, the month you most collected was the 4th, with 6 key chains. All the others months collected less keys (2 on the 2nd, 4 on the 3rd and 2 on the 5th).
I hope it is understandable.
CORRECT ANSWER:ITS 4 MONTHS
EXPLANATION: AS YOU CAN SEE THE PERSON WHO FIRST DID THE QUESTION HAS HORRIBLE REVIEWS AND ISN'T TRUST WORTHY, AS YOU CAN SEE I HAVE THE CORRECT ANSWER.