the remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock.
Answer:
The value is 
Explanation:
Generally the reaction between oxygen and magnesium is

Generally from the law of mass conservation in a chemical reaction we have that

Here
is the mass of magnesium
is the mass of oxygen
is the mass of magnesium oxide
So

=> 
=> 
Answer:
the answer is d
Explanation:
It migrates to coastal areas during the winter months to catch fish.
The mass of 1 mole of an element is its atomic weight on the Periodic Table in grams.
1g = 1000mg
The mass of 1 mole of Kr = 83.80g Kr
Convert mg Kr to g Kr.
398mg Kr x (1g/1000mg) = 0.398g Kr
Convert g Kr to mol Kr.
0.398g Kr x (1mol Kr/83.80g Kr) = 4.75x10-3mol Kr