A、In the 1920’ s. B、In the 1930’ s. C、In the 1940’ s. D、In the 1950’ s. C

Can you imagine ice that does not melt and is not wet? Have your ever heard of dry ice? Dry ice is made by freezing a gas. It is quite different from ordinary ice which is simply frozen water. Dry ice was first manufactured in 1925. It has since fulfilled the hope of its invent or. It can be used for making artificial fog in the movies. When steam is passed over dry ice, a very dense vapor rises. It can also be used for destroying insects in grain supplies. It is more practical than ordinary ice because it takes up less space and it is 142 degrees colder. Since it turns into steam, instead of melting into water, it is cleaner to use. For these reasons, it is extremely popular and many people prefer it to ordinary ice. Dry ice is so cold that if you touch it with your bare fingers, it will burn you.