The outermost electronic configuration of the last element of the p-block in the 6th period is represented by:

1. 7s27p6

2. 5f146d107s27p0

3. 4f145d106s26p6

4. 4f145d106s26p4

HINT: The last element in 6th period is Radon (Rn)

 
Explanation:
Each period starts with the filling of electrons in a new principal energy shell. Therefore, the 6th period starts with the filling of the 6s-orbital and ends when 6p-orbitals are completely filled.
In between 4f and 5d-orbitals are filled in accordance with the Aufbau principle. Thus, the outmost electronic configuration of the last element of the p-block in the 6th period is 6s24f145d106p6 or 4f145d106s26p6.