Practice Test RC "LED" vs "LCD"

[lianpan.sg]

Hi,

Could anyone help me out on interpreting this sentence below?

In LEDs, or light-emitting diodes, two different semiconductor materials are layered together: n-type, in which mobile electrons carry negative charge, and p-type, in which “holes” in an otherwise bound sea of electrons carry positive charge.

Answer for the detail question:
“Bound” means “restricted or confined to a specified place.”The use of the word “otherwise” sets up a contrast between the holes, which, it can be inferred, are UN-bound, and the bound sea of electrons around them.

If this is the case, shouldnt the sentence be written as " holes and otherwise bound sea of electrons..."

Thank you.

[tommywallach]

No. The sentence you wrote has no meaning at all. The use of otherwise is always in that format. For example:

It was an otherwise normal day, but for...

See, we've now set up a contrast. This means "The day was normal in every way EXCEPT for..."

-t