Heating a certain pure solid completely decomposes it into a solid and a gas, each of which is also a pure substance. Which of the following is/are reasonable conclusions regarding these observations?
1.The solid is a compound and the gas is an element.
2. At least one of the products is an element.
3. The original solid is not an element.
A. 1 only
B. 2 only
C. 3 only
D. 1 and 2
E 1, 2, and 3
