Take three test-tubes. Fill each other with water. Label them A, B and C. Keep a snail in test-tube A, a water plant in test-tube B and in C, keep snail and plant both. Which test-tube would have the highest concentration of Carbon dioxide.

Living organisms use oxygen and release CO2 during respiration.

Test tube A consists of snail which continuously uses the oxygen produced and releases carbon dioxide.

Hence, test tube A will have the highest concentration of carbon dioxide.

cramming before a final is bad because it makes a student's stress level higher. students who embrace cramming to get through a final exam week find themselves struggling to perform consistently, once the brain adjusts to prolonged sleep deprivation.