characters versus arrays in c

Why do 1, 2, and 3 work when 4 generates a segmentation fault? (See below.)

char c[10];
char* d;

1.
scanf("%s", &c);
printf("%s\n", &c);

2.
scanf("%s", c);
printf("%s\n", c);

3.
scanf("%s", &d);
printf("%s\n", &d);

4.
scanf("%s", d);
printf("%s\n", d);

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