Which of the following are the correct reasons for the anomalous behavior of lithium?

a.  Exceptionally small size of its atom

b.  Its high polarising power

c.  It has high degree of hydration

d.  Exceptionally low ionisation enthalpy

Choose the correct option
1. (a, b)
2. (b, c)
3. (c, d)
4. (a, d)

Hint: Lithium size is the smallest in its group and 

Although Li exhibits, the characteristic properties of alkali metals it differs at the same time in many of its properties from alkali metals.
The anomalous behavior of lithium is due to the extremely small size of lithium and its cation.
On account of its small size and high nuclear charge, lithium exerts the greatest polarising effect out of all alkali metals on negative ions.