How to filter column based on aggregate function in sql

ques) 1. Write a query that determines counts of every single column. Which column has the most null values?

I have written query for the first part the output looks like

Now how to filter column which has maximum null value i.e. giving column name which has min value?

In this question, you are supposed to answer the column name just by look at the count values in the first step.

We have not learnt about other methods of handling columns separately in a way from where you can get this answer.