1. What kind of mistakes is he making?
2. What kinds of mistakes is he making>
3. What kinds of mistake is he making?
4. What kind of mistake is he making?
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Which expressions are grammatical? Which one is commonly used?
All are correct except for 3.
1, 2, and 4 are commonly used.
1. The first question, "What kind of mistakes is he making?" is grammatically correct. It is asking about the type or category of mistakes that a specific person is making. The use of "kind" suggests that there may be multiple categories of mistakes.
2. The second question, "What kinds of mistakes is he making?" is also grammatically correct. It is asking about multiple categories or types of mistakes that the same person is making. The use of "kinds" instead of "kind" suggests that there are more than one specific type of mistake.
3. The third question, "What kinds of mistake is he making?" is grammatically incorrect. The plural noun "kinds" does not agree with the singular noun "mistake". It should be "What kind of mistake is he making?" to maintain grammatical agreement.
4. The fourth question, "What kind of mistake is he making?" is grammatically correct. It is asking about the specific type or category of mistake that a person is making. This question suggests that there is only one specific type of mistake being referred to.
Regarding which expression is commonly used, it depends on the context and personal preference. Both "What kind of mistakes is he making?" and "What kinds of mistakes is he making?" are commonly used and understood. The choice between using "kind" or "kinds" depends on whether you want to emphasize one specific category of mistakes or multiple categories of mistakes.