Answer:
a. Grisly.
Step-by-step explanation:
The sentence reads-
The ____ murder shocked the small town.
Now, using the options provided, it is possible and also valid to use the word annoying/ recent/ immoral in the blank space. All of them makes perfect sense and complete meaning to the other words in the sentence. But, considering the effect it produced on the people, it will be best to use the word 'grisly'. This word induces the worse of the worse results, something akin to barbaric or hideous. This word produces the most shocking reaction for the action, which is "shocked the small town".
Thus, the answer is -
The grisly murder shocked the small town.