reserve T for non empty TopSpace,
  A, B for Subset of T,
  F, G for Subset-Family of T;

theorem
  for A being Subset of T st A is closed holds A is F_sigma
proof
  let A be Subset of T;
  assume A is closed;
  then reconsider F = {A} as closed countable Subset-Family of T by Th20;
  take F;
  thus thesis by ZFMISC_1:25;
end;
