Here are the correct answers for each sentence:
- A(n) architect designs the building for a new opera house. (Option a)
- A(n) structural engineer tests whether concrete will be a strong foundation. (Option c)
- A(n) construction worker may be tasked to build an opera house. (Option d)
So the filled sentences would be:
- A(n) architect designs the building for a new opera house.
- A(n) structural engineer tests whether concrete will be a strong foundation.
- A(n) construction worker may be tasked to build an opera house.