Which function's domain consists of all real numbers greater than 3?

You don't show any choices but there are many functions which have the domain restricted as you stated.

A few would could be y=√ (x-3) as there would only be imaginary solutions when x≤3. Or y=ln (x-3) for another for the same reason as above.

So from your choices, look at which ones don't produce a real value for y when x≤3