真的? 
Really? *“真的吗?”。询问对方的语气，也常说Oh, really?
He's 38. (他38岁。)
Really? (真的?)
Are you sure? *“敢肯定吗?”，想要确认的心情，要比上句稍强。 
你是认真的吗? 
Are you serious?
I want to break up with you. (我想和你分手。)
Are you serious? (你是认真的吗?)*有些怀疑对方的语感。
开玩笑呢吧? 
Are you joking?
I quit my job. (我把工作辞了。)
Are you joking? (开玩笑呢吧?)
Do you mean it? (是真的吗?)
Are you kidding? (是说着玩吧?) *kid 常来表示“耍弄，开玩笑”。 
我怀疑。 
I doubt it. *表示对别人的话抱有怀疑的心情。
Do you think you'll get a raise? (你觉得你能涨工资吗?)
I doubt it. (我怀疑。)
It's doubtful!
I don't think so. (我不这样认为。)
I wouldn't bet on it.
It's chancy. *俚语。
It's iffy. *非常随便的说法。 
听起来可疑。 
It sounds fishy to me. *fishy 除了表示“鱼的，像鱼的”之外，它还有“靠不住的，可疑的”意思。
What do you think? (你怎么想?)
It sounds fishy to me. (听起来很可疑。)
It sounds suspicious to me.
It sounds funny to me.
Something's fishy.
I smell a rat. *smell a rat 为短语，表示“感到有可疑之处”、“事情很可疑”的意思。
我不信他的话。 
I won't buy that story. *此处的buy表示“相信(believe)，当真”，而不表示“买”，口语中常用。
He said she is his sister. (他说她是他的妹妹。)
I won't buy that story. (我不信他的话。)
I won't buy that story. (我不会信他的话的。)
But, it's true. (可那是真的呀。)
I don't buy it.
I won't believe that story. 
你认为她是当真的吗? 
Do you think she's serious?
She told me she likes you. (她告诉我她喜欢你。)
Do you think she's serious? (你想她是认真的吗?) 
我不把他的话太当真。 
I don't take him too seriously.
I don't pay much attention to what he says. *pay attention to...“对……严加注意”、“对……留意”。
I don't take him very seriously. 
我不相信他。 
I don't believe him.
I don't believe him. (我不相信他。)
What makes you say that? (你为什么这么说呢?)
I don't trust him.
I don't think he is telling the truth. (我认为他没说真话。)
I think he is lying. (我认为他在说谎。) 
有这么好的事! 
It's too good to be true. *直译是“说得太好了”，表示事情或情况好得过分。
I won two tickets to Hawaii! (我赢了两张去夏威夷的票。)
It's too good to be true. (有这么好的事!)
It's so unbelievably good that there has to be something wrong. (哪有这么便宜的事!)
Nothing this good ever happens, it must be a mistake. (不会有这么好的事，一定是搞错了。)
It can't be! It's too good to believe! (怎么可能!好得让人难以置信。)