b. Yes because it passes the vertical line test. Any vertical line moving horizontally across the graph intersects only one point on the graph at a time.
c.
Domain: all real numbers
Range: all real numbers greater than or equal to 4
d.
Domain: all real numbers greater than or equal to 4
Range: all real numbers
e.
See pic below.
f. No because it does not pass the vertical line test.
I am sure this is a personal question, what do you think you would see if you would be able to travel within the multiverse, no one can answer that for you its your opinion :)