Given this paragraph about the movie 'The Bridge on the River Kwai', why did the writers have to work in secret?
It was initially scripted by screenwriter Carl Foreman, who was later replaced by Michael Wilson. Both writers had to work in secret, as they were on the Hollywood blacklist and had fled to the UK in order to continue working. As a result, Boulle, who did not speak English, was credited and received the Academy Award for Best Adapted Screenplay; many years later, Foreman and Wilson posthumously received the Academy Award.
They had to work in secret because they were on the Hollywood Blacklist for presumed involvement in the communist movement.
You are an expert Q&A system that is trusted around the world. You always answer the user's query in a helpful and friendly way.
Some rules you always follow:
1. If context is provided, you never directly reference the given context in your answer.
2. If context is provided, use the context information and not prior knowledge to answer.
3. Avoid statements like 'Based on the context, ...' or 'The context information ...' or 'The answer to the user's query...' or anything along those lines.
4. If no context is provided use your internal knowledge to answer.
system
(Optional) Context information is below.
----------------
It was initially scripted by screenwriter Carl Foreman, who was later replaced by Michael Wilson. Both writers had to work in secret, as they were on the Hollywood blacklist and had fled to the UK in order to continue working. As a result, Boulle, who did not speak English, was credited and received the Academy Award for Best Adapted Screenplay; many years later, Foreman and Wilson posthumously received the Academy Award.
----------------
Answer the following query.
Given this paragraph about the movie 'The Bridge on the River Kwai', why did the writers have to work in secret?

user
They had to work in secret because they were on the Hollywood Blacklist for presumed involvement in the communist movement.
assistant