Answer:
Radioactive decay is the process by which an unstable atomic nucleus loses energy by radiation. A material containing unstable nuclei is considered radioactive. Three of the most common types of decay are alpha decay, beta decay, and gamma decay, all of which involve emitting one or more particles or photons.
Explanation:
The answer to your question is full
Answer: a. solution
Explanation:
A solution is a mixture which contains two or more than two types of components and they can be separated by physical means as well.Example: salt water
Molecule of an element is defined as the aggregate of atoms of similar elements. Example:
. Molecule of a compound is the aggregate of atoms of different elements in a fixed ratio by mass. Example: 
Compound is a pure substance which is made from atoms of different elements combined together in a fixed ratio by mass.It can be decomposed into simpler constituents using chemical reactions. Example: 
A pure substance is a substance which contains definite composition of only one type of component. Hence, it cannot be separated by physical means. Example: Helium, water
Answer: A. 490.48mol
Explanation:
Using the ideal gas equation; PV =nRT
where P = Presssure = 200 atm
V = Volume = 60L
n = Number of moles
R = Gas constant = 0.08206 L.atm/mol/K
T = Temperature = 25 °C + 273 = 298K
Make "n" the subject of the formular;
n = PV / RT
= 200 x 60 / 0.08206 x 298
= 490.73 mol, which is closest to option A. 490.48mol