Students make errors while solving mathematical problems because they make alternative interpretations of concepts in their attempt to make meaning. This is the correct answer because it accurately captures one of the main reasons why students make mistakes in math.

Misinterpretation of Concepts:
- When students encounter a new mathematical concept, they may not fully understand its meaning or how it applies to different problems.
- Students often rely on their prior knowledge and experiences to make sense of new concepts, but this can lead to misconceptions and errors.
- They may interpret the concept in a different way than intended, leading to incorrect solutions or approaches to problems.
- For example, when learning about negative numbers, students may mistakenly interpret them as simply "less than zero" without understanding their role in real-world situations or in relation to other numbers.

Alternative Strategies:
- Students may also develop alternative problem-solving strategies that differ from the standard methods taught in class.
- This can be due to a lack of understanding or a desire to find a more intuitive or familiar approach.
- While some alternative strategies may be effective, others can lead to errors and confusion.
- For instance, when solving an algebraic equation, a student might use a different method for simplifying expressions, which can result in incorrect solutions.

Lack of Practice:
- While practice is important in developing mathematical skills, it is not the primary reason for errors in problem-solving.
- Students who practice regularly may still make mistakes if they have misunderstood a concept or are using alternative strategies.
- Practice alone cannot address these underlying issues and may even reinforce misconceptions if students are repeatedly practicing incorrect methods.

Socio-economic Status and Textbooks:
- Socio-economic status and the availability of multiple textbooks are not directly related to students making errors in mathematical problem-solving.
- While these factors can influence overall academic performance, they do not specifically impact the interpretation of mathematical concepts or the use of alternative strategies.

In conclusion, students make errors while solving mathematical problems because they make alternative interpretations of concepts in their attempt to make meaning. This highlights the importance of providing clear explanations, addressing misconceptions, and promoting a deep understanding of mathematical concepts to minimize errors in problem-solving.