Find the Domain and the Range of the Relation $( - \infty , \infty )$

Find the domain and the range of the relation. Also determine whether the relation is a function.
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A) Domain: $( - \infty , \infty )$ , range: $( - \infty , \infty )$ ; function
B) Domain: [3], range: [3]; not a function
C) Domain: $( - \infty , \infty )$ , range: [3]; function
D) Domain: [3], range: $( - \infty , \infty )$ ; not a function