Which is the first enzyme to mix with food in the digestive tract?

What would happen if green plants disappear from the earth?

$(a)$ What is the nature of food coming from the stomach?
$(b)$ Mention any two structural modifications in the small intestine which help in the absorption of food.

What is the function of platelet cells in blood?

“All plants give out oxygen during day and carbon dioxide during night”. Do you agree with this statement? Give reason.

Which of the following statement$(s)$ is (are) correct?
$(i)$ Pyruvate can be converted into ethanol and carbon dioxide by yeast.
$(ii)$ Fermentation takes place in aerobic bacteria.
$(iii)$ Fermentation takes place in mitochondria.
$(iv)$ Fermentation is a form of anaerobic respiration.