Explanation:

Correct Answer is (c). Replace ‘themselves’ by ‘himself’. As the main subject is ‘The officer’ which is a singular noun and by sub-verb agreement rule, nouns/pronouns, connected with ‘with’, ‘along-with’, ‘together with’ ‘as well as’, ‘like’, ‘unlike’, ‘besides’ etc. take the verb after them according to the first noun. Hence option ‘C’ has the error.