A class games.cards.Poker is correctly defined in the jar file Poker.jar. A user wants to execute the main method of Poker on a UNIX system using the command：java games.cards.
Poker What allows the user to do this？（）

A.put Poker.jar in directory /stuff/java， and set the CLASSPATH to include /stuff/java
B.put Poker.jar in directory /stuff/java， and set the CLASSPATH to include /stuff/java/*.jar
C.put Poker.jar in directory /stuff/java， and set the CLASSPATH to include /stuff/java/Poker.jar
D.put Poker.jar in directory /stuff/java/games/cards， and set the CLASSPATH to include /stuff/java