Professionalism is the key to success ?

I would say the key to success is hard work and effort, but everyone has their own opinion of things

C: by choosing to end the sentence in a preposition.

Explanation:

 In order to avoid overly formal language, a writer could revise the sentence by moving the preposition "on" which was placed before "which", therefore ending the sentence with this preposition. Prepositions normally precede nouns or pronouns, and wre considered ungrammatical to end sentences with them, but they are now accepted in colloquial form . So, in informal English , the sentence becomes: Mr. Richardson is shopping for the perfect shelf to display his bowling trophy on.