respiratory and circulatory digestive and respiratory digestive and urinary urinary and circulatory
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Which two systems are involved when waste and water are removed from blood as it flows through the kidneys?
Possibilities:
- respiratory and circulatory
- digestive and respiratory
- digestive and urinary
- urinary and circulatory

urinary and circulatory