Final answer:
The student's inquiry is unclear without additional context on the type of reduction being asked about. It relates to either percent composition or percent yield, both of which involve calculations of percentages in chemistry. The law of definite proportions ensures the same proportion by mass of elements within a compound, but more information is necessary to provide an exact answer.
Step-by-step explanation:
The student's question regards the proportion of the partial reduction in a pure substance. To determine what they might be asking, it seems to be related to the percent composition, which is the percentage of each element present in a pure substance, or possibly the percent yield which is the ratio of the actual yield to the theoretical yield, expressed as a percentage.
However, the question is vague and does not provide sufficient information to determine exactly what reduction they are referring to. Normally, reduction in chemistry can mean the gain of electrons of an element (reduction in oxidation state), or the reduction in mass or concentration of a substance.
The law of definite proportions states that a chemical compound will always have the same proportion by mass of its elements, regardless of the amount of chemical compound present. If the student is referring to the reduction in mass while maintaining the same proportion of elements, then according to the law of definite proportions, the reduction proportion could be any of the options given (25, 50, 75, or 100 percent), as long as the percent composition remains constant.
For a better answer, more context or information is required regarding the type of reduction the student is asking about. If they can provide additional details, it would be possible to calculate or provide a more concrete answer. Absent of that, there is not enough information to definitively answer the question posed.