关于一道C++的 常整型数问题！

答案是错的。正确答案是A，B也勉勉强强算可以。D是绝对不行的，D是浮点型（float）。详情可以参考C++官方网站如下几行（英文）：
The exponent, if present, specifies the magnitude of the number as a power of 10, as shown in the following example:

18.46e0 // 18.46
18.46e1 // 184.6

The exponent may be specified using e or E, which have the same meaning, followed by an optional sign (+ or -) and a sequence of digits. If an exponent is present, the trailing decimal point is unnecessary in whole numbers such as 18E0.

我这里有一份我翻译的中文的版本，但是暂时不知道到哪里去了……
而A则是字面值长整型常量，具体英文解释如下：

To specify an unsigned type, use either the u or U suffix. To specify a long type, use either the l or L suffix. For example:

unsigned uVal = 328u; // Unsigned value
long lVal = 0x7FFFFFL; // Long value specified
// as hex constant
unsigned long ulVal = 0776745ul; // Unsigned long value

选A
C和D 不加以解释。
B是字面常量，对于一个整