Mastering Java: The Ultimate Quiz for 'Thinking in Java

The method used to make a JFrame visible is setVisible(true). This method sets the visibility of the frame to true, making it appear on the screen. Option A, showFrame(), is not a valid method for JFrame. Option C, displayFrame(), is incorrect as the method to display a frame is not specific to JFrame and can be used for other types of components. Option D, openFrame(), is incorrect as it is not a valid method for JFrame. Therefore, the correct method to make a JFrame visible is B, setVisible(true).