ing-column-types-9 </td>
   <td style="text-align:left;"> exercise </td>
   <td style="text-align:left;"> read_csv(file = "data/ex_2.csv") </td>
  </tr>
  <tr>
   <td style="text-align:left;"> controlling-column-types-10 </td>
   <td style="text-align:left;"> exercise </td>
   <td style="text-align:left;"> read_csv(file = "data/ex_2.csv", col_types = cols(.default = col_character())) </td>
  </tr>
  <tr>
   <td style="text-align:left;"> controlling-column-types-11 </td>
   <td style="text-align:l