In the following sentence, a bracketed verb phrase creates a subtle tense and structure problem. Choose the option that best improves the bracketed part, or select no improvement if the original is correct. I wish I (knew what was) wrong with my daughter.

Introduction / Context:
This question examines the use of wish clauses and tense sequence in English grammar. The sentence expresses a present regret or desire about not knowing something that is currently true. The structure I wish I knew what was wrong with my daughter is a standard way to express such a feeling. The learner must decide whether any proposed change improves the sentence or whether the original structure is already correct.

Given Data / Assumptions:

• The main clause is I wish I knew, which expresses an unreal wish about a present situation.
• The subordinate clause is what was wrong with my daughter, referring to a present problem.
• The options attempt to change the auxiliary verb and tense in different ways.
• The context suggests that the speaker currently does not know what is wrong.

Concept / Approach:
In English, wish followed by a past simple tense often expresses a present unreal situation or regret. For example, I wish I knew means I do not know now, but I want to. When the content of the wish refers to a continuing situation, we still commonly use the past simple. The reported clause can use was even though the problem is present, because the entire structure is shifted back in tense to mark unreality. Therefore, I wish I knew what was wrong is a natural and correct expression.

Step-by-Step Solution:
Step 1: Recognise that the sentence expresses a present wish about knowledge the speaker does not have. Step 2: Recall the rule that wish plus past simple is used for unreal or hypothetical situations in the present. Step 3: Observe that knew in the main clause correctly applies this rule. Step 4: Note that the clause what was wrong is part of the same hypothetical framework, so the backshift to was is acceptable and idiomatic. Step 5: Compare the alternatives, which either misuse had known, mix tenses incorrectly, or produce ungrammatical past forms like had knew.

Verification / Alternative check:
We can compare parallel sentences for confirmation. For instance, I wish I knew where she was is standard English. The pattern I wish I knew what was wrong follows the same logic. On the other hand, I wish I had known what is wrong mixes past perfect with a present clause, which does not match the intended meaning. That combination would suggest regret about not knowing something at a past time, which is different from the current wish about the present situation.

Why Other Options Are Wrong:
Option a, had known what is, uses the past perfect had known, which is normally used to refer to an earlier past event before another past event. This does not match the speaker's present wish. Option b, knew what is, creates an odd mixture of past and present in the same clause without the usual backshift, so it sounds less natural. Option c, had knew what was, is grammatically incorrect, because knew already functions as a past form and cannot combine with had in that way. Option e, had known what was, again suggests regret about knowledge in an earlier past time, not a present wish.

Common Pitfalls:
Many learners think that whenever a sentence contains wish, they must use past perfect, but that is true only when the speaker is regretting a past event. For unreal present situations, the correct tense is normally past simple. Another pitfall is assuming that present time reference always demands is inside the clause, but in wish structures, was is acceptable and even common in informal and standard contexts.

Final Answer:
The original sentence already uses the correct wish construction, so there is no improvement needed, and option d is correct.