如何给孩子讲清楚这道题---**Question Number:** 3 **Question Stem:** 下列计算34-7的方法中，错误的是（ ）。 (Translation: Among the following methods for calculating 34-7, which one is incorrect ( )?) **Options and Associated Calculations:** * **Option A:** * Calculation shown: ``` 34 - 7 = 27 / \ 20 14 | _ 7 ``` * Description: Calculation method shows 34 decomposed into 20 and 14. Below the 14, there is an operation indicated by a line and the number 7, suggesting 14 - 7. The result 27 is shown above. * **Option B:** * Calculation shown: ``` 34 - 7 = 27 / \ 24 10 | _ 3 ``` * Description: Calculation method shows 34 decomposed into 24 and 10. Below the 10, there is an operation indicated by a line and the number 3, suggesting 10 - 7 = 3 (implicitly). The result 27 is shown above. * **Option C:** * Calculation shown: ``` 34 - 7 = 33 / \ _ 4 3 | 30 ``` * Description: Calculation method shows 34 - 7 = 33. Below 34, there is a decomposition structure. The number 30 is below a blank space linked to the top number. The number 4 and 3 are shown above 30 and linked to the top number. This setup is unclear but shows a different decomposition method and an incorrect result (33 instead of 27). **Marked Answer:** ( A ) is marked in the blank space of the question stem.