以下4个程序中，不能实现两个实参值进行交换的是 ( )。
A．void swap (float *p, float * { float *t ,a; t = &a; t = p; *p = *q; *q = *t; } void main () { float x = 8.0;y = 9.0; swap (&x, &; cout＜＜x＜＜", "＜＜y＜＜end1; }
B．void swap (float *p, float * { float a; a = *p; *p = *q; *q = a; } void main() { float x = 8.0;y = 9.0; swap (&x, &; cout＜＜x＜＜", "＜＜y＜＜end1; }
C．void swap (float *p, float * { float x; x = *p; *p = *q; *q = x; } void main() { float a,; *a = 8.0;*b = 9.0; swap (a, ; cout＜＜x＜＜", "＜＜y＜＜end1; }
D．void swap (float &p, float & { float a; a = p; p = q; q = a; } void main() { float a = 8.0,b = 9.0; swap (a,; cout＜＜x＜＜", "＜＜y＜＜end1; }