$[10$pts total$]$ In Python, you have the following data frame stored in variable $"$X$".$ The first row shows the

column headings:

more rows...

a$.[5$pts$]$ Give the Python code needed to return a new data frame containing only fields A and $C,$ and

only rows where or $A==1$

b$.[5$pts$]$ For most machine learning techniques, what preprocessing would be required for column $"$C$"?$

Explain, not code.