Answer:
The correct answer would be - floor opening.
Explanation:
A floor opening is an opening or entry or hole that is at least 12 inches or more than that in the pavement, yard, platform, floor or anything in which someone or something can fall in it.
It is made for the entry or exit of person to fix anything under or above this pavement or platform. The best example of these floor openings is stair or ladder pit, manway hole, or hatchway.
Thus, the correct answer is opening - floor opening.
Answer: the antigens identify the foreign invader
The nervous system consist of the brain, spinal cord and nerve fibers. Exercise Improves the brain
