What does it mean that variables are case-sensitive?

When variables are described as case-sensitive, it means that the programming language distinguishes between uppercase and lowercase letters in variable names. This implies that "name" and "Name" are considered two separate and distinct variables, each capable of holding different values or data.

In programming contexts, this feature allows developers to use more descriptive variable names and to follow naming conventions that can improve code readability and maintainability. For example, a developer might choose "userName" for a variable that stores a user's name and "UserName" for a class name. By enabling the use of different cases, programming languages help prevent naming conflicts and make the code more expressive.

The other provided choices do not accurately capture the concept of case sensitivity. For instance, stating that all variables must be in uppercase or lowercase ignores the flexibility that case sensitivity provides. Similarly, suggesting that only numbers can be case-sensitive is misleading, as variables themselves, not numbers, are what exhibit case sensitivity.