In Python, you have the following data frame stored in variable $"$X$".$ The first row shows the column headings:

A B C D

$42"$QR$"51\mathrm{.}4$

$15"$WW$"1\mathrm{.}2$

$37"$AS$"13\mathrm{.}7$

$...$more rows...

b$.[5$pts$]$ For most machine learning techniques, what preprocessing would be required for column $"$C$"?$ Explain, not code.