Strange "cut" command's behaviour

Hi,

Suppose if I have a file having data like this:

$ cat file.txt
A
B C
D

And, if I do a cut operation like this:

$ cut -d" "  -f2 file.txt

The output is

A
C
D

This is the same for even if we try to get the field 3 with -f3 (assume line 2 has 3 fields : C E F).

The above output is applicable only when there is only one field per line.

But, if the file contains more then one field, like:

$ cat file.txt
A B
B C F
D E

Then, applying the command to fetch column 3 as:

$ cut -d" "  -f3 file.txt

results in:

 
F

Why this behavior?

man man cut ("cut")

 -f list         The list following -f is a  list  of  fields
                 assumed  to  be  separated  in the file by a
                 delimiter character \(see -d \); for instance,
                 -f1,7  copies  the  first  and seventh field
                 only. Lines with no field delimiters will be
                 passed through intact \(useful for table sub-
                 headings\), unless -s is specified.
 -n              Do not split characters. When -b list and -n
                 are  used together, list is adjusted so that
                 no multi-byte character is split.
 -s              Suppresses lines with no  delimiter  charac-
                 ters in case of -f option. Unless specified,
                 lines with  no  delimiters  will  be  passed
                 through untouched.