def preprocess_df(df):
    """
    Select the english captions and extract only the desired columns from the dataframe like 'Name' and 'Description'

    df: dataframe which contains the captions
    """
    df = df[df['Language'] == 'English'].copy()
    df['Name'] = df[['VideoID', 'Start', 'End']].apply(lambda x: x['VideoID'] + '_' + str(x['Start']) + '_' + str(x['End']), axis = 1)
    data = df[['Name', 'Description']]

    return data