Which of the following statements about a compound is true? a. only the chemical properties of a compound are usually the same as those of the elements from which it is formed. b. the physical and chemical properties of a compound are usually the same as those of the elements from which it is formed. c. only the physical properties of a compound are usually the same as those of the elements from which it is formed. d. the physical and chemical properties of a compound are usually very different from those of the elements from which it is formed.

The correct answer is D. The physical and chemical properties of a compound are usually very different from those of the elements from which it is formed.

If elements react together and form a compound, the properties of compounds are different from those of constituent elements. This is because a compound is made if different particles which are more than those in elements.
For example oxygen and hydrogen. Both are invisible gases when in a room temperature. Oxygen makes things burn while hydrogen causes an explosive. If they are mixed together there is an invisible gas but they can have a dangerous explosive.