Which statements concerning casting and conversion are true？

第1题：

Which statements concerning the switch construct are true？（）  

• A、All switch statements must have a default label.
• B、There must be exactly one label for each code segment in a switch statement.
• C、The keyword continue can never occur within the body of a switch statement.
• D、No case label may follow a default label within a single switch statement.
• E、A character literal can be used as a value for a case label.

第2题：

Which statements concerning the value of a member variable are true， when no explicit assignments have been made？（）  

• A、The value of an int is undetermined.
• B、The value of all numeric types is zero.
• C、The compiler may issue an error if the variable is used before it is initialized.
• D、The value of a String variable is "" （empty string）.
• E、The value of all object variables is null.

第3题：

第4题：

Which statement is true about the digital to analog conversion process？（）

• A、the two steps of digital to analog conversion are decompression and reconstruction of the analog signal
• B、the two steps of digital to analog conversion are decoding and filtering
• C、the two steps of digital to analog conversion are decompression and filtering of the analog signal
• D、the two steps of digital to analog conversion are quantization and decoding

第5题：

Which statements concerning the methods notify（） and notifyAll（） are true？  

• A、Instances of class Thread have a method called notify（）.
• B、A call to the method notify（） will wake the thread that currently owns the monitor of the object.
• C、The method notify（） is synchronized.
• D、The method notifyAll（） is defined in class Thread.
• E、When there is more than one thread waiting to obtain the monitor of an object， there is no way to be     sure which thread will be notified by the notify（） method.

第6题：

Which two statements are true about analog to digital conversion of voice signals for use in digital telephony networks？（）

• A、The three required steps in the analog to digital conversion are sampling，encoding，and compression.
• B、The three required steps in the analog to digital conversion are sampling，quantization，and compression.
• C、The three required steps in the analog to digital conversion are sampling，quantization，and encoding.
• D、The output of the sampling process is a pulse code modulation （PCM） signal.
• E、The output of the sampling process is a pulse amplitude modulation （PAM） signal.

第7题：

Which statements concerning casting and conversion are true？（）  

• A、Conversion from int to long does not need a cast.
• B、Conversion from byte to short does not need a cast.
• C、Conversion from float to long does not need a cast.
• D、Conversion from short to char does not need a cast.
• E、Conversion from boolean to int using a cast is not possible.

第8题：

第9题：

Which statements are true concerning NAT？ （）

• A、 NAT provides 1 to manyaddress mapping.
• B、 NAT provides 1 to 1 address mapping.
• C、 NAT is only useful forTCP/UDP and ICMP traffic.
• D、 NAT can be used for all IP traffic.

第10题：

Which of these statements concerning the collection interfaces are true？（）  

• A、Set extends Collection.
• B、All methods defined in Set are also defined in Collection.
• C、List extends Collection.
• D、All methods defined in List are also defined in Collection.
• E、Map extends Collection.