(b) Sieve tubes and companion cells
Explanation:
- Sieve tubes: Main conducting elements in phloem that transport food (mainly sucrose).
- Companion cells: Help in the functioning and loading/unloading of materials into sieve tubes by providing energy and support.
(i) Blood vessel A – It carries carbon dioxide rich blood to the lungs.(ii) Blood vessel B – It carries oxygen rich blood from the lungs.(iii) Blood vessel B – Left atrium relaxes as it receives blood from this blood vessel.(iv) Blood vessel A – Right atrium has thick muscular wall as it has to pump blood to this blood vessel.The correct statements are(a) (i) and (ii) only(b) (ii) and (iii) only(c) (ii), (iii) and (iv)(d) (i), (ii) and (iii).