Explain why this mapping is or is not a function

0(pointing to 1) 1
1(pointing to 2) 2
2(pointing to 1)
3(pointing to 2)
4(pointing to 1)

A. This is a function because every input maps to only one output.

B. This is a function because every output maps to only one input.

C. This is not a function because more than one input maps to an output.

D. This is not a function because more than one output maps to an input.***

Am I right?

2 answers

nope.
Each input must map to exactly one output. So, A.
Oh ok, Thank you!