1. 2 STUDENT WHEN PERFORMING EXPERIMENT FOR PROVING CO2 IS RELEASED DURING RESPIRATION.STUDENT A USES COTTON TO MAKE IT AIR TIGHT AND B USED WODDEN BLOCK FOR MAKING AIR TIGHT.

WHICH STUDENT WILL GET DESIRED RESULT? WHY? 

i think student b
 

Student B because wood will be more impervious to air than cotton. 

Using cotton plug instead of rubber cork is avoided since the partial vacuum will not be created in case of cotton, leaving the set-up airfill.
Hope dis helps thumbs up plz!

I believe student 'b' will get the desired result. Wood is denser compared to cotton, and would block the entry of any undesired air from the environment into the beaker where the plant is kept. Hope this answer was helpful :).