下面哪种方法可以避免编译器对结构体进行对齐优化？（）

struct {
       unsigned char head;
       unsigned char sector;
       unsigned char cylinder;
};

struct {
       unsigned char head;
       unsigned char sector;
       unsigned char cylinder;
}__attribute__((pack));

 struct {
       unsigned char head;
       unsigned char sector;
       unsigned char cylinder;
}__attribute__((packed));

struct {
       unsigned char head;
       unsigned char sector;
       unsigned char cylinder;
}__attribute__((aligned(0)));