你怎样察觉出那些50元面值的纸币是伪造的?用英语怎么说？

你怎样察觉出那些50元面值的纸币是伪造的?

How did you spot those fifties were counterfeited?

how

adv. 怎样，健康状况如何，到何种地步，以任何方式；n. 方法，方式；

例句
He showed how the rich and powerful can abuse their position.
他让我们看到有钱有势的人是如何滥用其地位的。

did

v. 做( do的过去式)，干，学习，研究；

例句
He did have a real knowledge of the country...
他对该国的确知之甚多。

you

pron. 你，你们，您们，各位，大家；

例句
I suggest you leave it to an expert...
我建议你把它留给专家来解决。

spot

n. 地点，场所，斑点，污点，[股票]现货，职位，职务；v. 弄上污渍，弄上斑点，污辱，玷污，认出，发现，散步；adj. 现场的，现货的，插播的；abbr. satellite positioning and tracking 卫星定位和跟踪；

例句
Vince is having a spot of bother with the law.
文斯惹上了点儿官司。

those

adj.& pron. that的复数；adj. 那些的，那；n. 那，那个( that的名词复数)，（指较远的人或事物）那，（指已提到过或已知的人或事物）那，（特指）那；

例句
We shall strike hard, without flinching, at terrorists and those who abet them.
我们要毫不退缩地严厉打击恐怖分子及其帮凶。

Fifties

n. 五十几，五十年代( fifty的名词复数 )；

例句
I probably look as if I'm in my fifties rather than my seventies.
我大概看上去像 50 多岁而不是 70 多岁。

were

be的过去时复数和第二人称单数形式，有时代替 was,用于条件从句、动词 wish 之后等；

例句
Shops, houses, and vehicles were set ablaze.
店铺、房子和车辆全都陷于火海。

counterfeited

v. 仿制，造假( counterfeit的过去分词 )；

例句
She counterfeited alarm when he confessed his love.
当他向她示爱时她假装惊讶的样子.