Answer:
The (stories) of Graham Greene probe the human psyche.
Step-by-step explanation:
In grammar, the subject of a sentence is the performer of the action.
There is a simple way to find out the subject of a sentence which is done by asking yourself, "What action is performed here?" "Who is the performer of the action?"
Asking this question will help you to get the subject of a sentence. So, from the sentence given, The stories of Graham Greene probe the human psyche.
If you ask, "What action is performed here?"
The correct answer would be storytelling
Now, "What probes the human psyche?"
The stories of Graham Greene