To answer this question, we need to analyze each part of the sentence to identify any errors. Let's go through each option:
Option A) a - This option is the correct answer. The error is in part (a) of the sentence. The error lies in the use of "not only." When using "not only," it should be followed by "but also" to maintain parallelism. In this case, "not only" is followed by "involved," but it should be followed by "involved" and then "in." Therefore, the correct form should be "not only involved in."
Option B) b - This option is incorrect because part (b) of the sentence does not contain any errors. The phrase "in her kidnapping" is correctly constructed.
Option C) c - This option is incorrect because part (c) of the sentence does not contain any errors. The phrase "in her murder" is correctly constructed.
Option D) d - This option is incorrect because the given sentence has an error in part (a), as explained above.
Therefore, the correct answer is A.