The calculus math classes, MA 1160 and MA 1161 (calc I), MA 2160 (calc II), and MA 3160 (multivariable calc), require that you enroll in corresponding recitation and lab sections. For example, if you are enrolling in R01 then you also will need to enroll in L01. R02 enrolls in L02, R03 enrolls in L03, etc. If you do not enroll in the corresponding recitation/lab sections then you will get a registration link error.