Answer:
Option C: In business class, Rita is learning to develop cost-effective marketing programs.
Step-by-step explanation:
-Option A is lacking one en dash. The correct usage would be: In physics class, Paolo is studying the strength-to-weigth ratio of building materials.
-Option B has one too many en dashes. The usage would be: In biology class, Tyra is working with an expensive-phase contrast microscope.
-Option C is lacking an en dash. The correct usage would be: In shop class, James is making a dining room table out of course-grained wood.