Onclick button disables checkboxes

Onclick button disables checkboxes

. .I couldn't find a proper answer for onclick function on a button
disables three checkboxes. . .
<input id="option" name="item_number" type="checkbox" class="ckbox"
value="1" onclick="this.checked=!this.checked;"/>
<input id="option" name="item_number" type="checkbox" class="ckbox"
value="1" onclick="this.checked=!this.checked;"/>
<input id="option" name="item_number" type="checkbox" class="ckbox"
value="1" onclick="this.checked=!this.checked;"/>
And the button to add onclick function already there are many onclick
functions.
<input type="button" class="button2" id="item2" value="Add to Cart"
Title="Add to Cart"
onClick="addItem_check('item_listing_100','ItemTable','100','Amul
Butter','500','g','150.00','1','kg','200.00','2','kg','250.00');
amul1.style.backgroundColor='#c2ed5c'; if(this.value=='Add to Cart')
{this.value = 'Remove from Cart'}; item2();"/>
So please give me a solution guys