You are logged in as user tux1, but now you want to switch to user tux2 using tux2’s environment.
How would you do this?

A.
su tux2

B.
su -e tux2

C.
su – tux2

D.
su -m tux2

E.
su -f tux2

Explanation:
from the man pages:
-, -l, –login Provide an environment similar to what the user would expect had the user logged in directly.
There are no -e or -f options and -m would not switch the environment (except PATH)