Consider the following Java variable names: I. 1stInstance II. basicInt% III. empName_ IV. addressLine1 V. DISCOUNT. Which option is correct?

To understand which variable names are valid in Java, it’s essential to recall the rules for naming identifiers. In Java, a valid variable name must start with a letter, underscore (_), or dollar sign ($). After the first character, it can contain letters, digits (0-9), underscores, and dollar signs. Variable names cannot contain special characters such as percentages (%) or start with a digit.

Looking at the variable names provided:

• "1stInstance" begins with a digit, which is not allowed.
• "basicInt%" contains a percentage sign (%), which is not a permitted character for variable names.
• "empName_" is valid because it begins with a letter and contains an underscore.
• "addressLine1" is valid as it starts with a letter and contains letters and digits.
• "DISCOUNT" is also valid as it starts with a letter and contains only uppercase letters.

Hence, the variable names "empName_", "addressLine1", and "DISCOUNT" are valid according to Java's naming rules. This makes the option that states only the third, fourth, and fifth names are valid correct.