D. Was my purpose for reading achieved?
A would not be suitable because asking yourself the subject of the text should be something you do before you read, in order to be prepared for the text and establish your purpose for reading it.
B would not be suitable because that, again, should be something you do before you read, in order to be prepared for what you do and do not already know about the material and establish your purpose for reading it.
C would not be suitable because, for the third time, you should ask yourself that question before you read the text in order to establish your purpose.
D is the only suitable answer because it allows you to reflect on your reading and determine if you have achieved your purpose for reading so you know whether or not you should reread the text.
