YDS 2015-2 Soru=17

Some aeroplanes waste valuable fuel. (17)----, there are
attempts to redesign such planes for maximum
efficiency. Recently, two engineers (18)---- planes from
the very beginning combining fuel efficiency,
aerodynamics and the necessities of goods, passengers
and fuel storage. Their final design seems to
(19)---- several elements found in birds. They examined
the three major parts that make a plane (20)---- it is:
body, wings and tail. They worked through all three
(21)---- turn, only opting for the design that would lend
their final product the maximum flight efficiency