What are the domain and range of the step function below?

a) domain= {all real numbers}, range = {all real numbers}
b) domain= {all real numbers}, range= {…-4,-1,2,5,…}
c) domain={…-5,-2,1,4,…}, range= {…-4,-1,2,5,…}
d) domain= {all integers}, range={all real numbers}