Can someone explain multiplicity of a zero?

Multiplicity refers to the exponents of the factors.  For example:

x³(x + 1)(x + 2)²(x² + 1) = 0

x:        has a multiplicity of 3 because its exponent is 3

x + 1:    has a multiplicity of 1 because its exponent is 1:  (x + 1)¹

x + 2:    has a multiplicity of 2 because its exponent is 2

x² + 1:    has a multiplicity of 1 because its exponent is 1: (x² + 1)¹

Hope this helped!

The correct answer is B) 
-3 < y ≤ 3

You can tell this by looking at the graph. The lowest that it goes is -3. You'll also note that the -3 has an open circle, which means that it isn't includes and thus needs a <.

The highest it goes it 3. You'll note that it has a closed circle, which means it is included and needs a ≤.