Which of the following statements is correct about natural language processing $($NLP$)?$

Select all that apply.

IBM Project Debater was close, however not a successful project in the field of natural language processing.

In natural language processing, an AI system can speak human language perfectly once it builds a corpus.

IBM Project Debater was a major step forward in the field of natural language processing.

Human language is complex, so machines require natural language processing systems to understand human language.