Source

File: wp-admin/includes/class-wp-comments-list-table.php

public function column_cb( $comment ) {
		if ( $this->user_can ) {
			?>
		<label class="screen-reader-text" for="cb-select-<?php echo $comment->comment_ID; ?>"><?php _e( 'Select comment' ); ?></label>
		<input id="cb-select-<?php echo $comment->comment_ID; ?>" type="checkbox" name="delete_comments[]" value="<?php echo $comment->comment_ID; ?>" />
			<?php
		}
	}