Python. This question is about reading files and detecting end of file. The following code is to display a file's contents to the screen. The condition of the while loop is not set. I leave a question mark$(?)$ instead. Please select a correct condition to read files until the end of file.

# Open the file

filename $=$ input$($Enter the filename: $\text{'})$

in $\_$file $=$ open$($filename$,\text{'}$r$\text{'})$

# Prime the loop by reading the first line

line $=$ in$\_$file.readline$()$

# If the line exists, print it and read the next line.

while $?$:

print$($line$,$ end$="")$

line $=$ in$\_$file.readline$()$

# Close the file

in$\_$file.close$()$

A$.$ line!$=$

B$.$ line $!=""$

C$.$ line $!=$ eol

D$.$ line $==\text{'}\text{'}\text{'}\text{'}$