20. The following grep command will search the f.txt file for lines containing any number of spaces (at least one space must be present other characters should be on those lines).

a) Grep ‘ *’ f.txt
b) Grep ‘^ *$’ f.txt
c) Grep ‘^ *$’ f.txt
d) Grep -E ‘^ * $’ f.txt
e) Grep ‘ +’ f.txt
f) Grep -e ‘^ + $’ f.txt

e) Grep ‘ +’ f.txt