Show that the set of all bit strings (strings of 0's and 1's) is countable. In order to show the set of all bit strings is countable, we must find a function f from ℤ+ to the set of all bit strings with certain properties. Which of the following properties are needed? (Select all that apply.) f is a well-defined function from ℤ+ to the set of all bit strings f is onto f is one-to-one f is symmetric f is reflexive f is transitive