This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General physiology, Subject name: Physiology
The first step for lymphatic vessels to remove excess fluid from interstitial tissue spaces is by 
Select and explain. 
A. Generating a lower intravascular than tissue hydrosta tic pressure, B. Contracting and forcing lymph into larger lymphatics, C. Opening and closing one-way valves in the lymph vessels, D. Lowering the colloid osmotic pressure inside the lymph vessel
A: Generating a lower intravascular than tissue hydrosta tic pressure
Answer: A: Generating a lower intravascular than tissue hydrosta tic pressure 
Explanation: Although all of the choices are events that happen in lymph vessels, the first key event is lowering the lymphatic hydrostatic pressure to enable tissue fluid to enter the lymphatic vessel.