某文本型字段的值只为字母且不允许超过4个，则可将该字段的输入掩码属性定义为( )。
A．AAAA
B．LLLL
C．CCCC
D．####
参考答案：B
______ you are in trouble, let me know. I'll give you a hand. [ ]
A. Whenever
B. Wherever
C. However
D. Whatever
