You find a rock sample with radioactive atoms present. 25% of the original radioactive atoms were present, how many half lives have passed

Im literally taking a test that my teacher made and i have no idea what the answer is

Explanation:

if you know your abc's you should be able to get your answer or just use google

all these collisions do one thing, and that thing is explained in the last option. when dusst, rocks and ice collide, they harden and form giant layers of rocks or hard ice.

d)   to harden materials to form different parts of earth’s layers

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bioteacher101