D, light can travel in the air or a vacuum and the speed is constant whether the light source is stationary or moving.
the human body is always at work and using all organs the bodys largest organ is the skin
There could be multiple answers to this due to where the hair like fibre is. if it is on a bacteria to aid movement it is called a flagella. if it is attached to a cell, for example in the throat or oviduct, it is called a cilia
