Abundance ratios of C,N, Na, and Mg/O as a function of remnant mass for a zero-metallicity 15 M_⊙ (top) and 35 M_⊙ (bottom) star (Limongi & Chieffi 2012) after the explosion (bold sold lines, left y-axis). The abundance ratio X/O is defined as the difference between the predicted and observed [X/O] values. The right y-axis shows postexplosion interior profiles of ⁴He (dotted black line), ¹²C (red), ¹⁶O (cyan), ²³Na (blue), and ²⁴Mg (orange).