What is the correct way to open a file data.txt in Python for reading?

A$)$ file $=$ open$("$data$.$txt$","$r$")$

B$)$ file $=$ open$("$data$.$txt$",$ mode$=$"read"$)$

C$)$ file $=$ open$("$data$.$txt$",$ "read"$)$

D$)$ file $=$ open$("$data$.$txt$")$

Answer: A$)$ file $=$ open$("$data$.$txt$","$r$")$