You can use the following tags:
<b>
<strong>
<i>
<em>
<a>
<p>
<span>
<br>
<u>
<p style="font-weight: normal">for non-bold text</p>
<p style="font-size: x-small">for a smaller font size</p>
<p style="display: none;"> for hiding this text </p>
Hyperlink
You can also embed a hyperlink:
<a href="www.namewebsite.com">Name link</a>
Besides, you can also have a hyperlink to be opened in a new tab, this way your respondents can continue the page of the survey as well:
<a href="www.namewebsite.com" target="_blank">Name link</a>