Final answer:
'Bad smells' in program code refer to code that is difficult to understand, hard to modify, and prone to bugs.
Step-by-step explanation:
'Bad smells' in program code refer to code that is difficult to understand, hard to modify, and prone to bugs. These are code characteristics that make the code less efficient, maintainable, and reliable. For example, code that is difficult to understand can be overly complex, lacking proper comments, or using cryptic variable names. Code that is hard to modify may have tightly coupled components or lack clear separation of concerns. Code that is prone to bugs may have poor error handling or lack proper input validation.