сделать 1. The translucent properties of this ceramic (1)(first/discover) by NASA ceramic engineers.

2. They (2) (carry out) research to (3)(develop) tough new materials when they suddenly (4)(notice) that light (5)(pass) through one of the ceramics.

3. Now, however, the ceramic (6)(commonly utilise) by dental engineers for (7)(make) protective braces, or restraints, for children’s teeth.

1) a) were first discovered b) had been first discovered c) have been first discovered

2) a) carried out b) had carried out c) were carrying out

3) a) developing b) develop c) have developed

4) a) have noticed b) noticed c) were noticing

5) a) passed b) was passing c) had passed

6) a) commonly utilised b) was commonly utilised c) is commonly utilised

7) a) making b) being made c) make

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