Write the Word or Phrase That Best Completes Each Statement

Write the word or phrase that best completes each statement or answers the question.
All answers to questions asking for a combining form must be written in the combining form style, meaning word root/combining vowel. For example, a combining form meaning heart is cardi/o. All answers to questions asking for a suffix must be written in suffix form, meaning a hyphen before your answer. For example, the suffix meaning cell is -cyte. All answers to questions asking for a prefix must be written in prefix form, meaning a hyphen after your answer. For example, a prefix meaning two is bi-.
Do not capitalize any of your answers or include a period at the end of your answer. The computer will not recognize your answer as correct if it is written in any other style.
-A combining form that means sound is ________.