有本书上说：除去通常目前时和通常过去时外，在 appear 和 seem 之后，通常不可以省去 to be：
He appears / seems ill. 他好像病了。
He seems a fool. 他好像是个笨蛋。
It seems / seemed a real bargain. 这东西好像非常实惠。
我的疑问是：仿佛 appear 和 seem 也只可以用于通常目前时和通常过去时吧？难道还可用于除通常目前时和通常过去时以外的其他时态？假如可以，那 appear 和 seem 都可用于什么时态呢？
▲假如 appear 和 seem 是用作连系动词，它确实主如果用于通常目前时和通常过去时，但有时也用于完成时态（目前完成时和过去完成时）。如：
The past few days have seemed comparatively flat and empty. 过去这几天好像比较平淡无聊。
She had been surprised at how amiable and polite he had seemed. 看到他这样平易近人、彬彬有礼，她很惊讶。
That expressionless face had seemed deep and mysterious. 那张毫无表情的脸看起来深沉而又神秘。
At one point he had seemed a likely candidate to become Prime Minister. 他一度看上去是个适合的首相人选。
He was surprised they had married — they had seemed so different. 他两个居然结婚了——这让他很惊讶，由于他们实在是太不同了。
The woman he had seen performing on stage was in actuality quite older than she had seemed. 他所见的那个在舞台上表演的女性实质年龄比看起来要大不少。
For many days now Buddy and Joe had appeared to be more and more tangled up in secrets. 这类天巴迪和乔仿佛变得愈加神神秘秘。
注：上面的例子也说明，除去通常目前时和通常过去时外，在 appear 和 seem 之后的 to be 也可以省去的。
▲另外，seem 和 appear 的完成式还可用于情态动词之后。如：
It must have seemed a miracle to the onlookers. 对于旁观者来讲这一定像是奇迹。
The scar added interest to a face that otherwise would have appeared too bland. 这处伤疤为本看上去平淡无奇的脸增添了些吸引力。
▲注意，若 appear 不是用作连系动词（譬如用作实义动词，表示“出现”“演出”“出席”“出庭”“出版”等），则其时态使用方法比较灵活。如：
Slogans have appeared on walls around the city. 标语已出目前全城周围的墙上。
She is currently appearing at the Liverpool Playhouse. 她现在正在利物浦剧院演出。
He’s appearing at a local folk festival tonight. 他将在今晚出席当地的民俗节日活动。
Harris disappeared from the scene as suddenly as he had appeared. 哈里斯忽然出现，又忽然消失了。
