Answer: Option (c) is the correct answer.
Step-by-step explanation:
When an element has more than one number of shells then there will be decrease in force of attraction between the nucleus and outermost electrons.
This decrease in force of attraction is known as shielding effect as more is the number of shells present in an element greater will be the shielding effect.
This means that larger is the size of an atom greater will be the number of shells present in it. Hence, greater will be its shielding effect.
For example, Li, K, Rb, and Na are all group 1 elements out of which Rb is largest in size.
Electronic configuration of rubidium is
![[Kr] 5s^(1)](https://img.qammunity.org/2019/formulas/chemistry/high-school/9y48fkg81lq19xxfl5kkctjnmoqi9ir2gl.png)
.
Thus, we can conclude that out of the given options rubidium is the element that would exhibit the greatest shielding effect.