Why five zang-organs can be in the state of fullness but not solidity?

Why five zang-organs can be in the state of fullness but not solidity?
A.Because five-zang organs are solid organs.
B.Because five-zang organs can be touched by our hands.
C.Because the organs only store essence but not excrete it.
D.Because they accord their anatomical characteristics.
正确答案：Because the organs only store essence but not excrete it.