2. A survey was conducted
Tungsten steel alloy has high strength, good ductility and toughness.
4. Accidents may cause personal injury or property damage.
There is a lot to explain about UFOs.
The purpose of census analysis is to predict the future population.
The voltage must be checked regularly.
Welding proved to be an unsatisfactory property.
This method can eliminate motor damage.
If a scientist wants to prove a theory, he must obtain sufficient evidence.
Instruments and machines need to be adjusted frequently before use.
12, radiation research found that ...
13, a new system is proposed on the basis of recent research.
14, sulfuric acid is used to remove the surface impurities of the sample.
15, in the early report, the new equipment design and new manufacturing methods were summarized.
Has been described.
16, these theories may be proved wrong or confirmed.
17, no expectation.
18, the experiment was postponed because of unfavorable weather conditions.