In Which of the Following Scenarios Does the Extrinsic Reward

In which of the following scenarios does the extrinsic reward undermine the student's motivation to learn?

A) Douglass read dozens of books as quickly as he could because he wanted to win a race with classmates to read the most books by the end of the year.
B) Sally practiced singing several holiday songs because she loved to sing and wanted to join the school choir.
C) Randy competed against other students for a position on the debate team because he thought that such an opportunity would help him pursue a career as a lawyer.
D) Wayne used to dislike writing because he had trouble spelling words correctly, but now he enjoys writing with the help of the spell-check on his computer.