Answer:
The answer is below
Explanation:
The half life of a substance is the time required by that substance to reduce to half of its initial value. The half life is calculated using the formula:

Given that t = 87 years, half life = 29 years, therefore the quantity of strontium-90 left is:

That is one-eight of Strontium 90 would be left after 87 years
Answer:
A
Explanation:
dahil glasses Endrie jay inted you
This is cyclic change because the population is consistently going up and back down.
Answer:
A rock is a collection of minerals. In a cooling lava, mineral crystals do not have time to form and are very small. The chemical composition will be the same as if the magma cooled slowly. Existing rocks may be heated enough so that the molecules are released from their structure and can move around.
Explanation: