Answer:
SI system i think it is right
Mercury a terrestrial. It isn't made of gas.
Answer:
527 Hz
Solution:
As per the question:
Beat frequency of the player, 
Frequency of the tuning fork, f = 523 Hz
Now,
The initial frequency can be calculated as:


when

when

But we know that as the length of the flute increases the frequency decreases
Hence, the initial frequency must be 527 Hz
Lithium is to be considered as an ION
Atom is defined as its natural state where it will have all its electrons present in its shell
Since in this case Lithium is giving its electron so after giving the electron it will become an ion
Compound is the combination of two or more different atoms
Molecules is the combination of same type of atoms
So here answer must be
<em>C) ion</em>