Assuming the answer is a grammatically correct sentence, you can greatly reduce the search space by only testing grammatically correct sentences:

• Grab all unique eight word sentences from a large corpus (wikipedia, ebook collection, etc.)
• Perform part-of-speech tagging on each sentence and retain all unique tagsets
• For each tagset, iterate through all possible combinations of matching words for the parts of speech. Wordlists for parts of speech can be obtained from WordNet.