Different fibers have different uses, and can be found in both clothing and food.不同的纤维有不同的用处，在衣服和食物中都能找到。

fierce adj.凶猛的

We saw fierce tigers at the zoo.我们在动物园里见到了凶猛的老虎。

file n.①档案②行列，纵队

I accidentally dropped a stack of file，and all the papers fell out.我不小心掉了一摞档案，里面的所有文件都掉了出来。

All the ships are sailing in single file.所有船只成一列纵队向前航行。

I file the reports in the drawer.我把抽屉里的报告进行了归档。

filter vt.过滤

We filter our drinking water.我们过滤我们的饮用水

The filter of a cigarette helps prevent some of the harmftil substances from entering the body.香烟的滤嘴有助于防止有害物质进人身体。

finance n.财政，拨款

We’ve had some difficulty raising finances for the project.我们在为这个项目融资时遇到了麻烦。

Joe financed his girlfriend’s study abroad, but she never came back.乔资助他女朋友出国留学，结果她一去不复返了。

flame n.火焰，光辉

Flames roared out of the burning house.火焰从那栋着火的房子里蹿出来。

flash n.闪光；闪现

It is common knowledge that a flash of lightning is seen before a clap of thunder is heard.先看到闪电，后听到雷声，这是常识。

The driver flashed the blinker to indicate a left turn.司机打转向灯来示意要向左转。

flavor n.味，风味

The drink has the flavor of grapes.这杯饮料有葡萄的味道。

Joey’s mom flavored the chicken with sugar to make it sweet.乔伊的妈妈用糖来给鸡肉调味，让它变得香甜。

flee v.逃跑

The thieves^feJ when they heard the alarm.小偷们听到警报声便逃走了。

flexible adj.易弯曲的，柔软的；变通的

Janet easily bent the flexible wire into a loop.珍妮特很轻松就把软线弯成了一个圈。