1. cardiology   production and application of low temperatures   fish   heart with its functions and diseases   sleep   Hint Half-n-half Clue   2. hydrodynamics   origin and development of human race   dance and ballet compositions   structure and functions of cells   mathematics of pressures of liquids in motion   Half-n-half Clue   3. acoustics   structure and properties of crystals   fish   society and family life   sound   Half-n-half Clue