Each red blood cell carries about 250 million molecules of hemoglobin.
how many molecules of oxygen could a single red blood cell deliver throughout the body if every hemoglobin molecule attached to four oxygen molecules?

1 Blood cell carries 250 million hemoglobin's, each hemoglobin carries 4 oxygen molecules. All we would have to do here is find out oxygen the 250 million hemoglobin's are carrying, if 1 carries 4 then we can multiply 250 million by 4  to get a whopping 1 billion oxygen molecules! So since 1 oxygen caries the 250 million which we multiplied right now, we have the answer!

1 Red Blood Cell carries 1 billion oxygen molecules! :D

Hope I was able to help. :)

"d.) carbon dioxide and hydrogen sulfide"