I'm not one hundred percent sure but wouldn't group selection be most harmful to the ecosystem because they cut down a group of trees all at once instead of one by one.
It means that it allows some things to pass through it but now all. (Liquids and gases)
False there are actually 5 types of biomes
Explanation:
The valency of the element is the measure of the combining power of the element with the other atoms when the element forms compounds or molecules.
<u>Thus, valency has to known to find the how the elements have been combined and how many electrons have been lost, gain or shared.</u>
Given that:
Element A has 3 valence electrons and element B has 2 valence electrons. To find the ionic compound, the valency of the cations and the anions are interchanged and are written in subscripts. Thus,
A B
3 2
Cross multiplying, we get the formula : 
<u>Hence, 3 is the subscript for Element B.</u>
Answer:
option c) 3 is the correct option
Explanation
as we know that 3rd principal energy level contains 3 sub levels,which are named as s,p and d. These sub levels further contain different numbers of orbitals,
and these sub levels can be termed as regions of probability of finding an electron, and each orbital may have a maximum number of two electrons in it.