Problem: Produce a sentence that would be considered grammatically acceptable

Answer: John has forgotten which player his son shouted at.

Problem: Produce a sentence that would be considered grammatically acceptable

Answer: I had hoped that it was true for many years that Rosa Luxemburg had actually defected to Iceland.

Problem: Produce a sentence that would be considered grammatically unacceptable

Answer:
Connie has become of the opinion that we should get out.