without end; limitless
able to be seen through
the area where one thing ends and another begins
from hot and humid zones
a need for something
Wind power is limitless and _____.
A photovoltaic cell has two different types of ____.
Many people are ___ to try new things.
The river marks the ___ between the two areas.
Glass is ___. It is clear enough to see things through.
A hydroelectric power station ___ water power into electricity.
The region's ___ on tourism has grown in recent years.
The world's demand ___ energy increases.
The photovoltaic cell offers a solution ___ the problem of a future energy shortage.
The sunlight is converted directly ___ electricity.
The cell is protected ___ damage.
The cell does not work as ___ (efficient) as it should.
Sand is made up mostly ___ silicon.
Photovoltaic cells have several advantages ___ fossil fuels.
We cannot wait a million years ___ more fossil fuels.
___ a few decades, petroleum supplies will run out.
The region's reliance ___ tourism is unwise.