What events in Donora, Pennsylvania, and London, England, in the 1940s and 1950s helped spur the clean-air movement?

passage of legislation

deadly smogs

construction of new high-polluting factories

mass protests

i think that you are smart and you should fit for it out

the law of original horizontality explains:   why rocks appear in layers. correct answer: b the law suggests that all rock layers are originally laid down (deposited) horizontally and can later be deformed.   the principle is used by geologists to make assumptions about the relative ages of sedimentary rocks.