Answer:
The concentration of KBr is
Explanation:
From the question we are told that
The mass of KBr is 
The molar mass of KBr is 
Volume of water is
This implies that the volume of the solution is 
The number of moles of KBr is

Substituting values

The concentration of KBr is mathematically represented as
It's B - convection that is correct...
ANSWER
2 valence electrons
STEP-BY-STEP EXPLANATION:
The electronic configuration is given below as

Looking at the configuration, you will see that the last energy carries 2 electrons
Hence, the valence electrons are 2
The oxidation of at least two atoms should change