Are string literals null-terminated?

Which of the following are null-terminated string?

char *str1 = "This is a string.";
char *str2 = "This is a string.\0";
char str3[] = "This is a string.";
const char *str4 = "This is a string.";
const char *str5 = "This is a string.\0";
const char str6[] = "This is a string.";

• All : a string literal is a null terminated string
• str2 and str5 have the particularity of being doubly null-terminated strings

Also :

• char *str1 should be const char *str1
• char *str2 should be const char *str2