multiple-choice (why backed up not set up)

In my Enflish textbook in a multiple choice task I have to choose one of the four variants. The correct one according to the keys is variant B. Could you please explain why B (not A) is the correct one.

We’re also keen to train the leaders of the future with our Leadership Development programme. It’s an intensive set of training courses …(backed)… up by specialist project work. After all, becoming a high flier in any company shouldn’t be about just waiting to shuffle up the ladder.

a. set; b. backet; c. held; d. kept.

Hi Ivret,

The choice of ‘b’ backed up is correct because it means ‘supported’. ‘Set up’ means ‘arranged’ and that is not appropriate when you consider the following sentence:

Alan,

Thank you very much.