填写缺失的部分，为 car1 变量赋值：
将“BMW”赋给 brand，将“X5”赋给 model，将 1999 赋给 year。
struct Car { char brand[50]; char model[50]; int year; }; int main() { struct Car car1 = {@(5), @(4), @(4)}; return 0; }
struct Car { char brand[50]; char model[50]; int year; }; int main() { struct Car car1 = {"BMW", "X5", 1999}; return 0; }