Answer:
Oral poliovirus vaccine or Sabin vaccine, named for its inventor American physician and microbiologist Albert Sabin, was developed. OPV contains live attenuated (weakened) virus and is given orally.
The answer is a because without them our veins would be dead
No problem
so
Chain 1. Sun -> Tomato plant -> Tomato -> You
The sun provides energy to the tomato plant which is used to grow a tomato which is eaten by you.
Chain 2. Sun -> Wheat -> Flour -> Bun -> You
The wheat uses the sun's energy to grow when the wheat is mature it is used to produce flour which is used to bake the buns for the hamburger which is then eaten by you again.
Chain 3. Sun -> Lettuce -> You
The lettuce grows and uses the sun's energy to live it is then eaten by you in the hamburger.
Hope this helps :).
