Ionic compound are those compounds which are made up of ions. The ion which has tendency to loose electrons is said to cation (positive charge) such as metals whereas ion which has tendency to gain electrons is said to anion (negative charge) such as non-metals.
Calcium nitrate is quite soluble in water due to very low lattice enthalpy in comparison to other ionic compound. With lower lattice enthalpy, less energy is required for the dissociation of calcium nitrate and it get dissolves in water than other three compounds. Moreover, hydration energy is higher for calcium nitrate which make its solubility higher in water than other ionic species.
Thus, 
is correct answer.
Answer:
I think section #3
Explanation:
When i was in science class in my memory it was always in that area
Answer :
(a) 0.0152
(b) 0.0000000778
(c) 0.000001
(d) 1600.1
Explanation :
Scientific notation : It is the representation of expressing the numbers that are too big or too small and are represented in the decimal form with one digit before the decimal point times 10 raise to the power.
For example :
5000 is written as 
889.9 is written as 
In this examples, 5000 and 889.9 are written in the standard notation and and are written in the scientific notation.
(a) 
The standard notation is, 0.0152
(b) 
The standard notation is, 0.0000000778
(c) 
The standard notation is, 0.000001
(d) 
The standard notation is, 1600.1
The average atomic mass of the element is the sum of the products of the percentage abundance of isotope and its mass number. Therefore, for atomic mass equal to 58.933, the most abundant isotope is cobalt-59. Thus, the answer is letter C.
I think because its the only one to be liquid at normal temperatures.
