Left panel: ratios of C₂H₂ to CO₂ integrated emission-line luminosities vs. submillimeter dust disk sizes from Table 2. Red markers denote lower limits for disks where CO₂ was not detected (VZ Cha, TW Cha, Sz 129, MWC 480) and upper limits for disks where C₂H₂ was not detected (AS 205S, MY Lup, Elias 27), and red X symbols denote disks where neither molecule was detected (RY Lup). Right panel: ratios of HCN integrated emission-line luminosities and cold 23.85 μm H₂O emission from A. Banzatti et al. (2025) vs. submillimeter dust disk size. Black markers are used to identify submillimeter substructures, as listed in Table 2.