C. Creative voice (VOC) format.
The VOC format is a proprietary data format defined by Creative Labs for use with their Soundblaster family of boards. It is widely used in DOS programs that make use of these boards, but is unusual on other platforms - including Windows. It is a sophisticated format which employs compression techniques to produce relatively compact files, and it is also possible to put tags that effect the playback into the data files (for example to pause the playback or repeat a section of the file). Although it is usually relatively easy to port a VOC sample to other formats, problems may be encountered if extensive use is made of these features.
FFMpeg apparently knows how to get files out of VOC format, but nobody's tried to get back in. That propriety tag is a problem.
Anyway, FFMpeg can be installed into your Audacity by getting it from here.http://audacityteam.org/download/