The aqeous extracts of some polymers when tested with chomotropic solution followed by addition of sulphuric acid and then heating to nearly 100 C gave dark violet colour. Which of the following cannot respond to this test?

• A. tpolyvinyl formal
• B. tpolyoxymethylenes
• C. turea-formaldehyde resisns
• D. tpolyacrylonitrile