Some buildings have electromagnets to hold fire doors open when the building is occupied. These magnets are mounted to the wall, like a doorstop, behind the door.
Thinking about the actions a fire alarm system would need to perform to control a fire,
what is the advantage of using a system like this to hold the doors? How might a system
like this be an advantage, or a disadvantage, in the event of a natural disaster?

the answer is f1 and d2 because if you put equal force on those two points the beam would balance trust me on this

as we know our atmosphere or air have different levels. every level has other gasses, and every gas has another permeability. when the light comes from lower permeability to higher permeability, it changes its direction. so that means that when the light comes from the moon to the earth, it changes it's direction many more times. it basically means that the shape of the light part of the moon is changed on the earth.

hope this ! this is not copied! search it up, it's free of plagiarism!

i think its c if i'm wrong