Braille is a method of producing text by means of raised dots that can be read by touch. A recent development in technology will allow flat computer screens to be made of a material that can be heated in patterns that replicate the patterns used in braille. Since the thermal device will utilize the same symbol system as braille, it follows that anyone who is accustomed to reading braille can easily adapt to the use of this electronic system. Which one of the following is an assumption on which the conclusion depends? ['People with the tactile ability to discriminate symbols in braille have an ability to discriminate similar patterns on a flat heated surface.', 'Only people who currently use braille as their sole medium for reading text will have the capacity to adapt to the use of the thermal screen.', 'Eventually it will be possible to train people to read braille by first training them in the use of the thermal screen.', 'Some symbol systems encode a piece of text by using dots that replicate the shape of letters of the alphabet.']