The diagram below shows part of the capillary bed in an organ of the human body. Some of the blood arriving at the capillaries at points labelled A, moves out into the spaces between the tissue cells. Study the diagram and answer the questions that follow:

(a) When the liquid from the blood surrounds the cells, what is it called?

(b) Name any one important component of the blood which remains inside the capillaries and fails to move out into the spaces.

(c) Some of the liquid surrounding the cells does not pass directly back into the blood but eventually reaches it by another route through vessel X. Name the fluid present in vessel X.

(d) State two important functions performed in our body by the fluid present in the vessel X.