Emission-line profiles of Model A in Cases I and II. The left panel in each row is the Ξ image. The values of (μ_U, ) and S_max are marked on the top of the Ξ images. The red dotted lines mark the LOS azimuthal angles φ_los. The four panels on the right in each row are the line profiles (blue solid lines) corresponding to different φ_los. The gray dashed lines are the profiles without spiral arms. The line profiles (mock mean and rms) of the spiral arms for Case I are provided in the upper two rows, and the profiles of Case II are shown in the lower rows.