专八改错题

We\'ve all used thermometers to measure temperature

but sometimes we need to measure temperature in places you （1） __places后加where

can\' t put a thermometer —— for example， inside a rocket engine.

One of the best methods for those really hard-to-get-to

place is based on laser spectroscopy. Light from a laser point（2） __place--places
-ing at the region of interest is absorbed by molecules and some（3） _ pointing--pointed
of it are

re-emitted back towards the source where it can be （4） _are--is_

measured. The re-emitted fight is shifted in frequency （changed

in wavelength） by amounts that depend on the molecule and

also the temperature and pressure of the surrounding gas be- （5） __also后加on

cause of collisions among the molecules. The single， sharp

frequency from the laser is thus smeared out into a whole

spectrum of frequency wh