Please read the following table in HTML format from a webpage and then answer the question in detail according to the table. Each table cell is defined by a <td> and a </td> tag. Each table row starts with a <tr> and ends with a </tr> tag. 'rowspan=m' and 'colspan=n' represents a cell spaning over 'm' rows and 'n' columns.

Webpage title:
City Nature Challenge
Table title:
Results
Table:
<table id='hittask' contenteditable='False'>
<tr> <th colspan=1 rowspan=1 > Year </th><th colspan=1 rowspan=1 > Cities participating </th><th colspan=1 rowspan=1 > Total observations </th><th colspan=1 rowspan=1 > Total species </th><th colspan=1 rowspan=1 > Total participants </th><th colspan=1 rowspan=1 > Results page </th></tr>
<tr> <td colspan=1 rowspan=1 > 2016 </td><td class="highlighted"  colspan=1 rowspan=1 > 2 </td><td colspan=1 rowspan=1 > 19,742 </td><td colspan=1 rowspan=1 > 3,152 </td><td colspan=1 rowspan=1 > 1,018 </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td class="highlighted"  colspan=1 rowspan=1 > 2017 </td><td class="highlighted"  colspan=1 rowspan=1 > 16 </td><td class="highlighted"  colspan=1 rowspan=1 > Over 125,000 </td><td colspan=1 rowspan=1 > 8,600 </td><td colspan=1 rowspan=1 > Over 4,000 </td><td colspan=1 rowspan=1 >  </td></tr>
<tr> <td colspan=1 rowspan=1 > 2018 </td><td colspan=1 rowspan=1 > 68 </td><td colspan=1 rowspan=1 > 442,518 </td><td colspan=1 rowspan=1 > Over 18,000 </td><td colspan=1 rowspan=1 > 17,329 </td><td colspan=1 rowspan=1 >  </td></tr>
</table>
Question:
How did City Nature Challenge perform in terms of expansion during the year 2017?
Answer:
In 2017, City Nature Challenge expanded to 16 cities and the participants collected over 125,000 observations.