Match the following.

1. to bend
-
opaque
-
2. not allowing light to pass through
-
refract
-
3. only partially clear
-

translucent
4. clear
transparent

1. to bend ==>  refract

2. not allowing light to pass through   ==>  opaque

3. only partially clear ==> translucent  

4. clear  ==>  transparent

Explanation:

1. to bend ==>  refract

When a substance (like water) or a surface (like a mirror) changes the direction of the light, it refracts it.

2. not allowing light to pass through   ==>  opaque

Usually a solid but also a thick/dark liquid can be an opaque barrier preventing the passage of light.

3. only partially clear ==> translucent  

Think about a white plastic or a film-coated glass pane, they will let you see there's light on the other side, but not letting it pass through completely.

4. clear  ==>  transparent

Think like a window or a anything similar that allows the light to pass through without any significant obstruction.

the mantle

explanation:

earth is divided into three layers: the crust or the outermost layer on which we live; the underlying, middle layer - the mantle - and the core (the innermost layer of earth).