Final answer:
The expression "confuse sb/sth with sb/sth" means to mix up or mistake one person or thing for another due to their resemblance or similarities.
Step-by-step explanation:
The expression "confuse sb/sth with sb/sth" means to mix up identities or characteristics of two or more persons or things. This often occurs when people or objects look alike, have similar names, or share some attributes that lead to confusion. For example, if you confuse a person with their twin, you are mistaking one sibling for the other because of their appearance. Similarly, you could confuse two similar concepts, like mitosis and meiosis in biology, if you don't remember their distinct characteristics.