Friction is a force that works against motion. While walking, friction helps us maintain our stability and prevents us from slipping. Friction also works the same way with cars and vehicles in general, preventing them from skidding and helping them stop when the brakes are applied. We also need friction to make a fire.
Answer:
An immune response is a reaction which occurs within an organism for the purpose of defending against foreign invaders. The first contact that an organism has with a particular antigen will result in the production of effector T and B cells which are activated cells that defend against the pathogen.
Explanation:
Answer:
Number of bacteria required 
Explanation:
Given -
Size of each bacterium 
micrometers long
These bacteria are arranged end to end.
The size of chain to be formed is equal to 
centimetres
Let us say that in forming a chain of centimetres nearly X number of individual bacterium are required.
hence, number of bacterium required to form centimetres chain can be represented as
Number of bacteria required
The placenta and the umbilical cord
<span>A fast-flowing river of air that forms when two air masses of very different temperatures meet is called a jet stream :)</span>
