The half-life of tritium or hydrogen-3 is it 12.32 years, after about 24.6 years how much of a sample of tritium remain unchanged?
a 1/3
b 1/2
c 1/8
d 1/4

The answer will be D, 1/4.

How you come to this conclusion( for future reference to anyone stuck on this ), is figure out how many half-lives have passed. In this case two half-lives have passed ( 24.6 is 12.32 + 12.32 ), so just put into your calculator 1/2 x 1/2 ( or .5 x .5 ). Make sure your answer is in fraction form, and you have your answer! Hope this helps any who may see this!

phylogenetic tree is the tree of life or evolution tree. it shows the different branches of evolution. the sequence goes like tissues - coelom - backbone - endoskeleton - segmentation

answer:

convection currents in the magma drive plate tectonics. heat generated from the radioactive decay of elements deep in the interior of the earth creates magma (molten rock) in the aesthenosphere. the aesthenosphere (70 ~ 250 km) is part of the mantle, the middle sphere of the earth that extends to 2900 km.