(1) This luminous body is bright, and its image is clearer. At the same time, its shape is regular, so it is easier to compare the sizes of images and objects with grid paper.

(2) As can be seen from the figure, the object is an inverted and reduced real image, so the object distance is more than twice the focal length, and the image distance is between one focal length and two focal lengths.

At this time, when the object distance increases, the image distance will be infinitely close to twice the focal length, but it will never reach twice the focal length, so the amplitude of the object moving to the left is greater than that of the image moving to the left; Therefore, when the luminous object is placed at point B, the distance between the object and the image will increase accordingly;

(3) When the candle is fixed, replacing it with a thinner convex lens is equivalent to replacing the experiment with a convex lens with a slightly larger focal length. Because the object distance is relatively reduced, it is necessary to increase the image distance to get a clear image on the screen, so the screen is far away from the convex lens (to the right).

(4) Because the seen image is inverted and is a real image, the imaging point is on the right side of the convex lens; The light emitted by a luminous object is convergent after refraction by a convex lens and divergent after passing through the imaging point, so the eyes must be in the divergent area outside the imaging point to see this image.

So the answer is: (1) It is convenient to compare the sizes of images and objects; (2)