Answers for "how to set the radio button clicked by default in html"

default checked radio button

<input type="radio" name="imgsel" value="" checked>

how to add select only one radio button in html

<input type="radio" name="nameA" id="nameA" value="nameA">
<label for="nameA">Choice A</label>
<input type="radio" name="nameB" id="nameB" value="nameB">
<label for="nameB">Choice B</label>