X-rays
used to measure bone density.
<u>Explanation</u>:
The bones density test measured by the X-rays, it measures the content of calcium and other bone minerals that are packed into the segment of bone. Most commonly used parts of bone for testing are spine, hip, occasionally and the forearm. It is generally done to know the chances of osteoporosis. More the bone minerals, more will be density. More density means the higher bone strength. Before the test, a person should avoid having calcium supplement.
By dating the rocks in the ever-changing crust, as well as neighbors such as the moon and visiting meteorites, scientists have calculated that Earth is 4.54 billion years old, with an error range of 50 million years.
Just follow the rock cycle.
<span>(1) Rock is broken down </span>
<span>(2) Regolith is eroded/transported </span>
<span>(3) Regolith is dumped </span>
<span>(4) Layers begin to compact </span>
<span>(5) Sedimentary rock is buried and turned into metamorphic rock </span>
<span>(6) Metamorphic rock melts to magma </span>
<span>(7) Magma resurfaces as igneous rock</span>
Explanation:
The Precambrian covers almost 90% of the entire history of the Earth. It has been divided into three eras: the Hadean, the Archean and the Proterozoic. The Precambrian Era comprises all of geologic time prior to 600 million years ago.
