df is a Pandas data frame containing vehicle collision data. Column 'Speed Limit' gives speed limit values (such as 25, 35, etc.) Select the expression to produce a bar plot showing, for each of the distinct speed limit values in df, the number of times each value appears. Choose the correct choice

a. df['Speed Limit'].value_counts().plot.bar()

b. histogram(df['Speed Limit'])

c. df['Speed Limit'].vcounts().plot.bar()

d. plot.bar(df['Speed Limit'].value_counts)