B is correct. When the start() method is attempted a second time on a single Thread object,the method will throw an IllegalThreadStateException. (Although this behavior is specified in theAPI, some JVMs don't consistently throw an exception in this case). Even if the thread hasfinished running, it is still illegal to call start() again. A is incorrect because compilation will succeed. For the most part, the Java compiler onlychecks for illegal syntax, rather than class-specific logic. C and D are incorrect because of thelogic explained above.