This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Transpo Processes, Subject name: Physiology
[{'content': 'Which of the following substances crosses capillary walls primarily through water-filled clefts between the endothelial cells? \nSelect and explain. \nA. O2, B. CO2, C. CO, D. Glucose', 'role': 'user'}, {'content': 'Answer: D \nExplanation: Because O2, CO2 and CO are lipophilic, they cross capillary walls primarily by diffusion through the endothelial cell membranes. Glucose is water soluble; it cannot cross through the lipid component of the cell membrane and is restricted to the water-filled clefts, or pores, between the cells.', 'role': 'assistant'}]