【正确答案】LiI. It is composed of a very small cation and a very large anion and so is expected to have a smaller than extrapolated lattice energy. Thus the energy required to break up the lattice is lower and is easily provided by the hydration energy. Literature values of the solubility are Lii,433 g per 100 g water at 80℃ ;KI, 208 g per 100 g water at 100℃.