Inventions and discoveries. Grammar: Passive Voice. Form 9 (Karpyuk)

a) was designed and built

b) was designed and builed

c) were designed and built

a) are displayed

b) is displayed

c) was displayed

a) will be constructed

b) was constructed

c) were constructed

a) were called

b) was called

c) are called

a) is performed

b) was performed

c) are performed

a) are demonstrated

b) were demonstrated

c) was demonstrated

a) are discovered

b) was discovered

c) were discovered

a) is produced

b) are produced

c) was produced

a) was established

b) were established

c) is established

a) is used

b) are used

c) was used

a) are discovered

b) was discovered

c) will be discovered

a) are visited

b) is visited

c) were visited