表示在不确定的过去发生的某一动作对现在仍有影响。谓语动词一般为短暂性动词。这种完成时态往往较难理解，也常常和一般过去时混淆不清。

 
注：图中黑点表示过去某一时刻发生的动作；虚线表示过去发生的动作对现在仍有影响。
例句
a. He has broken his leg.
他跌断了腿。（言外之意是：Now he is still in hospital, so he can’t go for an outing with his classmates.他现在还在住院，所以不能和同学们一起去郊游。）
b. He broke his leg.
他腿摔断过。（单纯表示一种过去的经历，但现在腿已经好了。）
c. A modern girl went to the theatre with a vest and a pair of slippers. The ticket-examiner turned her away very politely, “Miss, NO ADMISSION WITH SLIPPERS.” “Really?” the girl took off the slippers and carried them in her hands, “Then I will go in bare-footedly.” “Oh, my god!” the ticket-examiner cried out,“Fortunately, I have not told her NO ADMISSION WITH A VEST.”
d. —What has happened to Jane? She is crying.
— She broke the dining-room window. She has to face the music（勇于承担后果） when her father gets home.
e. Mr. Odds works in a bank and lives on his own. The only family he has is in the next town: his sister lives there with her husband, and her son,Mark. Last week Mr. Odds had a surprise. He drove home from the bank at the usual time, driving neither too slowly nor too fast; he parked his car where he always parked it, out of the way of other cars, and he went inside to make his evening meal. Straight away, there was a knock at the door. Mr. Odds opened the door, to find a policeman standing on the doorstep.
“What have I done wrong?” Mr. Odds asked himself. “Have I driven on the wrong side of the road? Has there been some trouble at the bank?
Have I forgotten to pay an important bill?”
“Hello, Uncle,” said the policeman, “My name’s Mark.”
欧兹先生在一家银行工作，独自生活。姐姐是他唯一的亲人，与其丈夫和儿子马克住在邻近的镇子上。上周欧兹先生遇上了一件让他吃惊的事。他照常从银行下班后开车回家，车速不快也不慢。他把车停在老地方，没有挡住其他车的路。然后进门就开始做晚饭。很快，就有人敲门。欧兹先生打开门，看见台阶上站着一位警察。
欧兹先生心想：“我做错什么了吗？是开车逆行了？是银行工作中出了问题？还是某个重要账单我忘了付钱？”
“你好，舅舅，”那位警察说道，“我是马克。”
f.You should have put the milk into icebox; I expect it______undrinkable by now.
A.became
B.had become
C.has become
D.becomes
正确答案：C
句意：你本该把牛奶放在冰箱里的，我想现在这牛奶已经不能喝了。
“牛奶变质”是过去某一时刻的动作，但其对现在有影响，即现在牛奶已经不能喝了。
这种现在完成时的特点下文将详细讨论
。