Read the following context and choose the best option to answer the question.
Context: Over the weekend I had thought about writing a whole post about the events of Saturday . They can be summed up in a paragraph though . I went to the library and put my car in the shop . The car needs to go back this Saturday so that they can finish the work since they had to order a part .
Question: Why do they need to take their car back to the shop ?
Options: 
A. None of the above choices .
B. They have been unable to drive their car until it 's fixed .
C. They needed to pay them for the other repairs .
D. Their car needs a new part installed in it .


D