the skeletal system the endocrine system the respiratory system the integumentary system
I am hesitating between 4 options to answer the following question, which option should I choose?
Question: Xylem cells have very thick walls. They make up most of a tree trunk and its branches. What system in vertebrates provides the same function as the xylem cells in a tree?
Possibilities:
- the skeletal system
- the endocrine system
- the respiratory system
- the integumentary system

the skeletal system