The breathing and respiration in woody stem of a plant takes place through :

One of the following animals does not use tracheae as the respiratory organs. This animal is:

The photosynthesis in a plant is not taking place during the day time if the plant is releasing:

One of the following organism does not depend on simple diffusion of gases for breathing and respiration. This organism is :

During marathon, we sometimes get painful contractions of leg muscles due to the accumulation of one of the following in leg muscles. This is :