Final answer:
To compile a Java class named Circle, use the command 'javac Circle.java' which creates a file named Circle.class containing the compiled bytecode.
Step-by-step explanation:
To compile a class in Java named Circle, you would use the javac command. The correct command is javac Circle.java. Following successful compilation, this command produces a file with the same name as the Java class, but with a .class extension, resulting in the file named Circle.class. The class file contains the Java bytecode that can be executed by the Java Virtual Machine (JVM). The correct answer is therefore a) javac Circle.java; Creates Circle.class.