Can you explain why it's Single instead of Head of household? Thanks!

Required information [The following information applies to the questions displayed below.] Elroy, who is single, has taken over the care of his mother Irene in her old age. Elroy pays the bills relating to Irene's home. He also buys all her groceries and provides the rest of her support. Irene has no gross income. . Assume the original facts except that Elroy has taken over the care of his grandmother, Renae, instead of his mother. What is Elroy ling status