在使用标准 C 库时, 下面哪个选项使用只读模式打开文件? fopen("foo.txt", "r") fopen("foo.txt", "r+") fopen("foo.txt", "w") fopen("foo.txt", "w+") fopen("foo.txt", "a")
fopen("foo.txt", "r")
fopen("foo.txt", "r+")
fopen("foo.txt", "w")
fopen("foo.txt", "w+")
fopen("foo.txt", "a")