Identify the meaningful variable names which can be used?Select one or more:a.$register_numberb.user1c.user named.1num

1. Break Down the Problem

We need to evaluate the variable names listed and determine which ones are meaningful and compliant with standard naming conventions in programming.

2. Relevant Concepts

• Meaningful Variable Names: They should describe the data they hold.
• Naming Conventions:
  • A valid variable name cannot start with a digit.
  • Variable names should consist of letters, numbers, and underscores but cannot include spaces or special characters aside from underscores.

3. Analysis and Detail

1. $register_number:

   • Starts with a dollar sign, which is atypical for many programming languages, but in some languages (e.g., PHP), this is valid for variable names. It's meaningful as it indicates that it's a register number.

2. user1:

   • This is a valid variable name. It is descriptive enough and indicates it might refer to a user. However, it could be more descriptive (e.g., userName).

3. user named.1num:

   • This variable name is invalid because it contains a space and a period. Valid characters should only include letters, numbers, and underscores.

4. Verify and Summarize

• $register_number: It can be considered meaningful but context-dependent based on the programming language.
• user1: Valid and somewhat meaningful but not descriptive enough.
• user named.1num: Invalid.

Final Answer

The meaningful variable names that can be used are:

• $register_number
• user1

The variable user named.1num is invalid and not suitable for use.