The elements of which of the following pairs are isobars?

• A. \({}_1^1H\) and \({}_1^3H\)
• B. \({}_1^1H\) and \({}_1^2H\)
• C. \({}_6^{12}C\) and \({}_6^{14}C\)
• D. \({}_{18}^{40}Ar\) and \({}_{20}^{40}Ca\)