Although I may be wrong, A- Human activity is the answer.
Answer:
you should sell your skateboards at $240
Explanation:
The price p to sell your skateboards for so that there is neither a shortage nor a surplus is the price that makes equal the quantity of sales and the quantity of supply, so p is equal to:
q (sales) = q (supply)
-3p + 700 = 2p - 500
700 + 500 = 2p + 3p
1200 = 5p
1200/5 = p
$240 = p
D) Guard against a short circuit electrocuting a user.
"The 4-wire setup is inherently safer and better able to prevent electrical shock, which in the case of a 220/240-volt circuit can be fatal."
It's known as Absolute Zero. On the Kelvin scale, 0 is the lowest that anything can reach in temperature. It's supposedly impossible to reach, but it's the known limit.
Change in state(from liquid to solid) and change in colour I believe.
