You are told that the function should have one input argument, but then you created a function with two input arguments: row and col. Here is a function with one input argument:
function out = odd_values(M)
... code here
end
Note that you do not need to assign to a temporary variable, you can simply assign to the output variable directly, so that code might look something like this:
out = M(1:2:end,1:2:end);
And now there is nothing else that you need to do except put it together.
