【单选题】
Mr. John was busy,()he could not come.
A、but
B、therefore
C、and
D、nor
A、but
B、therefore
C、and
D、nor
A、"john"=="john" B、"john".equals("john") C、"john"="john" D、"john".equals(newButton("john"))
A、"john"=="john" B、"john".equals("john") C、"john"="john" D、"john".equals(new String("john"))