Complete the sentences
Gravity is the ________ that pulls objects down towards the earth.
a. support
b. force
c. weight
b. force
The Chinese _______ kites centuries before flying machines were invented. (invent)
had invented
To soar
Maintain height in the air without flapping wings or using engine power.
Past perfect of ascend
had ascended
The ancient Chinese were _____ at kite making.
a. limited
b. stable
c. skilled
c. skilled
Leonardo da Vinci __________ a glider long before George Cayley successfully flew one. (design)
had designed
To flap
Move wings or arms up and down or side to side.
Past perfect of fly
had flown
Da Vinci's glider might have worked if its design had allowed for more ______ movement.
a. stable
b. limited
c. allow
a. stable
Before the Wright brothers tested the Flyer, they _____ how to build an engine powerful enough to lift it into the air. (work out)
had worked out
To be capable of
Be able to do something.
Perfect past continuous of flap
had been flapping
A pterosaur's bones and muscles were strong enough to _____ its great ______ in the air.
a. support / force
b. support / weight
c. allow / weight
b. support / weight
My sister ______ of learning to fly for as long as I can remember. (dream)
had dreamt
To adapt
Make suitable for a new use or purpose.
Past perfect of buy
had bought
Two _____ of reptiles are teeth and bony tails.
a. limits
b. designs
c. features
b. designs
Our whole family celebrated because my sister ______ her goal. (reach)
had reached
To evolve
Develop gradually from a simple to a more complex form.
Past perfect continuous of support
had been supporting