Arock has 12.5 percent of its original amount of potassium-40 remaining in it; potassium-40 has a half-life of 1.25 billion years. how long ago was the rock formed?

a. 1.25 billion years ago

b. 2.5 billion years ago

c. 3.75 billion years ago

d. 5 billion years ago

How does climate change cause the ocean's thermohaline current to slow down?

Afusion reaction takes place between carbon and another element. neutrons are released, and a different element is formed. the different element is a) lighter than helium.b)heavier than helium.c)the same weight as helium.d)dependent on the element that reacted with carbon.

The ammonia molecule in the diagram has the observed bond orientation because