Which of the following statements is correct?

Given below are two statements.
Statement $I$: Guard cells of stomata are kidney shaped in dicotyledons and dumbbell shaped in monocotyledons.
Statement $II$: In $Cyperus$,both kidney and dumbbell shaped guard cells are present.
In the light of above statements,choose the most appropriate answer from the options given below:

Which of the following is a respiratory gas?

What is the approximate amount of $CO_2$ eliminated by our lungs per day?

Which one of the following statements is incorrect?

If a large number of people are enclosed in a room,then