B AND C

@toyalli, happy to help. (B) says "incorporating humor into lectures can help professors to achieve the goals they have for those lectures." The key word here is "can," which suggests that incorporating humor is just one possible way (potentially out of many other ways, such as the use of visual aids) in which professors can accomplish their goals. (C) says "university professors can achieve the goals they have for their lectures only if they incorporate humor into them." The key phrase here is "only if," which we know introduces the necessary condition. Therefore, we can diagram (C) as: achieve goals -> incorporate humor. This means that incorporating humor is required for professors to achieve their goals; i.e. there are no other ways besides humor for professors to accomplish these goals. Ultimately, (B) and (C) differ significantly in their meaning regarding whether incorporating humor into lectures is just one possible way for professors to accomplish their goals or is the only way to do so. Does that make sense? Please let us know if you have any other questions!

It makes a lot of sense. Thank you so much especially for the prompt response ,highly appreciated