Answer:
D. Uranium-238
Explanation:
Explanation: Uranium- 238 is an unstable isotope of uranium. It is one of the most effective isotope used for radioactive dating in order to determine the age of a rock that is about billions of years old.
Modern cell phones dated back to the 70's more than 4 billion of 6 billion have cell phones and it was important because people could communicate with other people and if they need an emergency than can call BTW i think everyone should have a cell phone : )
The answer is D. It causes a the supply to go up for that product because there is very little of it and many people want it.
An open college is usually open admissions. That means that so long as you have a HS diploma or GED, you will get in. They let in everyone who applies, basically.
A selective college gets so many applicants that they have to screen out those who don't meet certain standards, so for a selective college, you'd need to be in a certain GPA level and/or have an SAT or ACT score that falls into a certain range to get in. They admit only a certain percentage of those who apply.
