Answer:
U shaped vallies?
Explanation:
(i dont know if this was one of the options)
The melting points of the compounds from the choices are listed below:
a. C25H52 -> +47 to +56 degrees celsius
b. Hg -> -38.83 degrees celsius
c. CaCl2 -> +772 degrees celsius
d. CuO -> +1326 degrees celsius
It is evident from the listed melting points above that mercury (Hg) has the lowest melting point. This is why mercury is liquid at room temperature.
Answer: 
Explanation:
Complete ionic equation : In complete ionic equation, all the substance that are strong electrolyte and are present in an aqueous state and represented in the form of ions.
Net ionic equation : In the net ionic equations, we do not not include the spectator ions in the equations.
Spectator ions : The ions present on reactant and product side which do not participate in a reactions. The same ions present on both the sides.
The complete balanced ionic equation will be:
In this equation,
are the spectator ions.
By removing the spectator ions from the balanced ionic equation, we get the net ionic equation.
The net ionic equation will be:

The answer is Vestigal. It is a type of anatomical structure that no longer serves any function. Over time they are no longer needed in the body. Apart from the wisdom tooth, another example would be the tail bone which has no use for humans.