Choose a, b, c to complete the sentences.

1. ----------------this law of mechanics one should know the theory well.
a. explaining b. to explain c. having explained
2. The plastics ------------ in our laboratory will replace iron and its alloys.
a. to be produced b. was producing c. have been produced
3. When ---------- the article he uses no dictionary.
a. translates b. translating c. translated
4. Physics is a science ------------ with phenomena of matter and energy.
a. deals b. dealing c. was dealing
5. The new instrument ------------ in our laboratory will be used in radio engineering research.
a. designed b. designing c. being designed
6. Every atom contains small particles ---------- kinds of electricity.
a. carrying b. carried c. carry
7. ------------ by young engineers the solar installations was used for melting metals.
a. designed b. having been designed c. having designed
8. The power station -------------- in our region will run on local coal.
a. built b. being built c. was built
9. A current ------------- through a conductor, a magnetic field is set up.
a. flowing b. flows c. having flown
10. The engine--------------, the operator started it.
a. is tested b. was testing c. having been tested
11. A sensitive receiver ----------------, the electric oscillations could be directly proportional to conductivity.
a. are built b. having built c. having been built
12. Other factors ----------------- constant, the current is known to be directly proportional to conductivity.
a. be b. being c. having been