Composite image of NGC 253, its environments, and the 86–101 GHz spectrum taken with ALMA ACA. Top panel: NGC 253 composite (RGB and Hα) image (credits: Terry Robinson). The overlaid dashed gray rectangle shows the total u − υ coverage consisting of 25 pointing mosaic obtained by the ACA 7-m for this work. We indicate dynamical environments present in the disk of NGC 253: the center, bar, ring, and spiral arms (Querejeta et al. 2021). Bottom panel: observed spectrum taken toward the center of NGC 253. Our observations cover frequencies from 85.7 to 101.5 GHz. The term spectral window i (i takes values from 1 to 4) is abbreviated as spw_i, and we mark all detected molecular emission lines.