Which body part transports oxygen, removes waste materials, and carries nutrients to the body as part of the circulatory system?

When the chemicals iron sulfide (fes) and hydrochloric acid (hcl) are combined, bubbles appear from the mixture. 1. does the appearance of bubbles indicate a physical or chemical change? 2. why do the bubbles indicate this change? 3. what property is this?

When did stem cell research become known ? who discovered stem cell? what experiments or studies have been conducted so far?

Animals that reproduce sexually either do it through external or internal fertilization. read the following statement and decide if it is true or false. birds reproduce through external reproduction which is because the female will then be able to protect the egg.