The following sentence has been divided into parts. One of them may contain an error. Select the part that contains the error.

Had she studied (A)/ more attentively, she (B)/ will have cleared (C)/ the entrance test. (D)/ No error

The correct answer is C.

Step-by-step explanation:
1. Identify the sentence structure: The sentence represents a third conditional construction, which is used to describe a hypothetical situation in the past and its past result.
2. Understand the third conditional formula: The standard structure of a third conditional sentence is:
If + Subject + Past Perfect (had + past participle), Subject + would have + Past Participle
Alternatively, when inverted (omitting "if"), the structure starts with:
Had + Subject + Past Participle, Subject + would have + Past Participle
3. Analyze the given sentence:
- The conditional clause: "Had she studied more attentively" (Correct inverted past perfect structure)
- The main clause: "she will have cleared the entrance test" (Incorrect modal verb)
4. Identify the error: The auxiliary verb "will" is used for future or real conditions (first conditional). To express a past hypothetical outcome that did not happen, the past modal "would" must be used instead.
5. Correction: The phrase "will have cleared" in part (C) should be replaced with "would have cleared" to make the sentence grammatically correct: "Had she studied more attentively, she would have cleared the entrance test."