Final answer:
The correct option is d.
Pure substances can be elements or compounds with a definite chemical composition. They cannot all be described by one single type of atom nor can they all be broken down into simpler substances; these traits only apply to elements.
Step-by-step explanation:
Bismuth (Bi), oxygen (O2), water (H2O), and ammonia (NH3) are all examples of pure substances. Answering the question regarding their characteristics, pure substances can be either elements or compounds.
- They are not limited to being compounds only, so the statement 'They can only be compounds?' is incorrect.
- Pure substances do have a definite chemical composition, meaning they contain a fixed proportion of elements in a specific arrangement. This is the defining feature of any pure substance, whether it is an element or a compound.
- Statements such as 'They cannot be broken down into simpler substances?' and 'They consist of only one type of element?' apply only to elements, not all pure substances. Elements like oxygen (O2) consist of one type of atom and cannot be broken down into simpler substances by chemical means.
- However, compounds like water (H2O) are made of more than one type of element, yet they still have a definite composition and can be broken down into their constituent elements (hydrogen and oxygen in the case of water).