D.) Cocina because taking in the feminine verb as Hermana means sister. Option A.) Cocinas is plural and in third person not making much sense. Option B.) Cocinamos would not be the correct answer as cocinamos means you and your sister are cooking and in the question it only mentions her sister. and finally option C.) Cocino is in first person and they are not talking about themselves they are talking about the sisters cooking.
You do not give money to the dog everyday, you give food to the dog everyday. I believe comer would not be conjugated since "Doy" is already in the "yo" form.
