Which if statement determines if the content of the string variable user$\_$unit is in the list accepted$\_$units?

accepted$\_$units $=[\text{'}$in$\text{'},\text{'}$cm$\text{'},\text{'}$mm$\text{'},\text{'}$km$\text{'},$ 'miles' $]$

if user$\_$unit in accepted$\_$units:

if accepted$\_$units in user$\_$unit:

if user$\_$unit $==($accepted$\_$units$)$:

if user$\_$unit $==x$ in accepted$\_$units: