Which organ acts as a pump in the circulatory system?

What is the name of tissues which transport:

(a) food in a plant?

(b) water and minerals in a plant?

What substance/substances are transported in plants by:

(a) xylem vessels and tracheids?

(b) sieve tubes (or phloem)?

Veins and arteries carry blood. Which of these carry blood :

(a) away from the heart?

(b) back to the heart?

Where does blood absorb oxygen?