Hello from MrBillDoesMath!
Answer:
The second choice, [1,2]
Discussion:
The key to this question is that we are looking for "local maximum". In the graph a local maximum, think "camel hump", occurs in the interval [1,2] -- but the global maximums, if there is one, appears to occur in x > 3 and x < -1
Thank you,
MrB