Answer:
(D) all of the above
Explanation:
All of the choices describe matter.
D, single replacement and exothermic. Single replacement because chlorine switches over to magnesium, exothermic because the reaction releases energy, evidenced by the test tube getting hot and the bark that's heard.
Answer:
#See solution for details.
Explanation:
-An electromagnet's field can be rapidly changed by just controlling the amount of current. The magnetic strength can be varied over time.
-This way, only a sufficient amount of current will be supplied to meet the needs.
-Unlike the electromagnet, the permanent magnet has a fixed magnetic strength and can only lift a specified weight.