要从磁盘上读入一个文件名为"c:\t1.txt"的顺序文件，以下正确的是（ ）

F="c:\t1.txt"Open F For Append As #2

F="c:\t1.txt"Open "F" For Input As #2

Open c:\t1.txt For Input As #2

Open "c:\t1.txt" For Input As #2