The same number of valence electrons exists in the same family of elements in the periodic table. In finding the answer to this problem, we just have to find the pair that belongs to the same family in the periodic table. The same family means same column. Among these, Oxygen and lead (Pb) are in the same family. This pair is the answer.
Answer:
$200.0 is the cost for installing a carpet for a room that measures 12.0 feet by 15.0 feet.
Explanation:
Length of the room = l = 15.0 ft = 
Width of the room = w = 12.0 ft = 
(1 yard = 3 feet)
Area of the room = l × w = 
Cost for installing a carpet for a room = $10 per square yard
Cost for installing a carpet for a room wit area 20.0 square yard :

$200.0 is the cost for installing a carpet for a room that measures 12.0 feet by 15.0 feet.
D is the only choice here that is appropriate given neutrons' lack of charge
Molarity is a measure of a solution's concentration calculation by getting the ratio of the number of moles of solute to the total volume of solution. This has a unit of M or molar, equivalent to mole/L.
It is more important and meaningful to know the molarity rather than if the solution is dilute or concentrated because molarity gives the QUANTITATIVE approach of knowing the concentration while the second one only gives us the QUALITATIVE description of the solution. Hence, we are able to calculate for other unknown parameters if we have the molarity known.