I would say D is the answer
Can you send me a picture of the page in the story that has that sentence in it and then maybe I will be able to answer you
During the postwar era c) former English colonies were breaking free and beginning to use the language in different ways around the world. This happened mostly during the 1960's and is now still an extremely popular language, due to globalization, as many jobs require it to be spoken whether you are living in an anglophone country or not.
An is the indefinite article in this sentence. A indefinite article is usually a or an (pronunciation word)
