Question

gap filling:
A balloon was originally an aerostat but later huge powered aerostats, characteristed (a)________rigid outer frame work and separate aerodynamic skin surrounding the gas bags,were produced,the Zeppelins(b)_______the largest and most famous.Then several accident, such as he Hindenburg disaalster in 1937,led to the demise of these airships.Now a day 'A balloon' is an unpowered aerostats,(c)_____an 'Airship'(d)______a powered one.
(a)1.at2.by3.for4.in
(b)1.were2.were being 3.being4.had been
(c)1.when2.which3.while4.where
(d)1.is2.was3.has4.are
Answer me please​

Answer 1

Answer:

1.by

2.w ere

3.w hile

4.is

Explanation:

answers are 10000% sure

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Answer 2

Answer:

1 by

2were

3while

4be

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