The correct answer is D) remove inside burrs with a reamer. After cutting a piece of tubing to be flared, the proper procedure is to first remove any burrs or jagged edges from the inside of the tube end using a reamer tool. This is important because any internal burrs or irregularities can interfere with the proper seating and sealing of the flared tube within the fitting. Removing the internal burrs helps ensure a tight, leak-free connection when the tube is flared and assembled. The other answer choices are incorrect because: A) crimping the tube end would deform the shape, B) flaring before removing burrs could lead to leaks, and C) roughing up the outside is unnecessary and could weaken the tube.