There are several different models that represent compounds. One type of model is shown. A large black sphere connected to 4 small blue spheres by 4 grey sticks.
What type of model is shown?

a structural formula
a chemical formula
a space-filling model
a ball-and-stick model

The representation described in the question is a ball and stick model.

Several kinds of models can be used to represent molecules. Models help us to accurately visualize what the molecule may look like. It shows the actual arrangement of atoms in the molecule in order to help us predict the possible reactions that the molecule may undergo.

A model which consists of spheres connected to each other is a ball and stick model. The spheres are the balls and they are linked to each other by the sticks.

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For those looking for the letter its D

Your welcome :)

a: 45.9 meters

b: 4.29 seconds

step-by-step explanation:

a: h(t)=1/2(-9.8)(3)^2+0(3)+90

h(t)=-4.9(3)^2+90

h(t)=-44.1+90

h(t)=45.9 meters

b: 0=1/2(-9.8)(t^2)+0t+90

0=-4.9t^2+90

-90=-4.9t^2

18.37=t^2

t=4.29 seconds

in the second question, the numbers aren't exact, but they're a close approximation.