B, because propel is to move forward.
America is built on the concept of capitalism, which has certainly taken a tole on those within it's government system. Big corporations control our country as we empty our pockets and fill theirs. Our society is no longer what it was intended to be. Our country was founded with the idea of freedom, now we are imprisoned by large corporations that grow bigger every minute. This causes us as individuals to become more materialistic and begin to devalue sentimental things. We have become slaves to our own system.
(I don't know how long it needs to be, but I can write more if you need)
It is safe when you have metal detector because it can also sensor thieves or shoplifter who wish to bring clothes outside the store. Metal detectors are useful to find hidden metal objects and can detect not just nearby but even metal objects buried underground.
The simple predicate is "did not know that"
