There are other isotopes of cerium which are radioactive. Different isotopes of cerium have different half-lives.
The half-life of an isotope can be found by studying how the number of atoms
changes over time.
Figure 7 shows how the number of atoms of cerium-148 in a 120 g sample changes
over time.
1. Determine the ratio of the number of cerium atoms in the sample when it was 100 seconds old compared with when the sample was 350 seconds old. Use data from Figure 7.
2. Determine the activity of the sample of cerium when the sample was 20 seconds old. Use Figure 7.

Neptune is the eighth planet from the sun. it was the first planet to get its existence predicted by  mathematical calculations  before it was actually seen through a telescope on sept. 23, 1846. irregularities in the orbit of  uranus  led french astronomer alexis bouvard to suggest that the gravitational pull from another celestial body might be responsible. german astronomer johann galle then relied on subsequent calculations to   spot neptune via telescope. previously, astronomer galileo galilei sketched the planet, but he mistook it for a star due to its slow motion. in accordance with all the other planets seen in the sky, this new world was given a name from greek and roman mythology — neptune, the roman god of the sea.

You would need to take a picture so i can see

We have no idea what the graph shows, or why it may be accurate,  because we can't see the graph.on a different subject, choice ' d ' is the only true statement among the choices.

The correct answer is  ait's a process by which rocks and minerals undergo in their composition^o^