A glass tube partially filled with water has one open end and one closed end (closed by the water surface). Such a tube behaves as a closed organ pipe, not an open organ pipe. Therefore, Assertion (A) is False. In a standing wave formed in such a tube, the open end is a displacement antinode because the air particles have maximum freedom to vibrate. The end in contact with water acts as a rigid boundary, so it corresponds to a displacement node because the water surface prevents the air particles from vibrating longitudinally. Therefore, Reason (R) is True. Hence, (A) is False but (R) is True.