Answer:
#2
Step-by-step explanation:
Function: A special relationship where each input has a single output.
#1 It's a function:
Jan → 150
Feb → 400
March → 430
#2 It's not a function:
Jan → 150
Feb → 400
March → 400 and March → 430 (two values for March)
#3 It's a function:
Jan → 150
Feb → 150
March → 400
#4 It's a function:
Jan → 400
Feb → 400
March → 400
