If an airplane circles a vessel 3 times，crosses the vessel’s course close ahead while rocking the wings，and heads off in a certain direction，what does this indicate（）.
A. The plane is in distress and will have to ditch
B. The plane is going to drop a package and wishes the vessel to recover it
C. Someone is in distress in that direction and the vessel should follow and assist
D. There is danger ahead and the best course is indicated by the direction of the aircraft
如果想在程序中反复使用一个数据“01/01/2000”，为了避免在编写程序时反复输入这个数据，也为了一次能够修改程序中所有用到这个数据的语句，可以采用（）
A. 将这个数据声明为字符串型常量，用一个常量标识符代表它。
B. 将这个数据声明为字符串型变量，用一个变量标识符表示它。
C. 将这个数据声明为日期型常量，用一个常量标识符代表它。
D. 将这个数据声明为日期型变量，用一个变量标识符表示它。
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