Because 私人guards 和員警 guards 看守 某個名人的宅邸, it is sure to keep his home and family safe 選項有:they are sure to keep his home and family safe surely, his home will be kept safe等等
倾向 surely 虽然有主动优于被动,但是Manhttan也有一小节提到Prefer被动的情况,例句: During this operation, new blood vesesels are inserted, by passing blockages. 点评是the writer intends to emphasize the action performed on the vessel and de-emphasized the surgeon. 这个句子里也是强调房子安全,而不强调动作发出者保安