With the fast development of computer and Internet technologies, traditional printed books ______ by the growing popularity of online reading of e-books.

A．are challenged

B．have challenged

C．are being challenged

D．have been challenged

在Foxbase中，下列说法（）是正确的。

A、字段类型有数值型、字符型、日期型、逻辑型、屏幕型

B、字段名是最长为10个字符的字符串

C、数值型字段最大宽度为19位数字，正负号和小数点也计算在内

D、每个数据库的字段个数在FOXBASE+中规定为最多为128个