how long from an file opened in the example below?

How to read a single line, no matter how long from an file opened in the example below?
<code>
$fp = fopen(“my_file.txt”, “w”);
</code>

A.
fgets($fp);

B.
fgets($fp, -1);

C.
fread($fp, 1024);

D.
fgetss($fp);

E.
None of the above