Unable to select just one checkbox

Unable to select just one checkbox

<input type =" checkbox " name =" q_4[] " value =" scales " />
<input type =" checkbox " name =" q_4[] " value =" horns " />
<input type =" checkbox " name =" q_4[] " value =" claws " />

key = "q_4[]";
value="horns";
$('[name="' + key + '"]' + '[value="' + value + '"]').prop("checked", true);

Thank you