Final answer:
The author develops the narrator's initial motivation to buy a car in the excerpt from 'Cape Coddities' through the children constantly begging him for one.
Step-by-step explanation:
The author develops the narrator's initial motivation to buy a car in the excerpt from 'Cape Coddities' through option b. The children of the narrator are constantly begging him for one. This is evident from the text where the narrator mentions that every time he comes back from the garage, the children are waiting eagerly asking if he has bought a car. This shows their persistent desire for him to buy a car.