Directions: In the question below, the 1^st and the last (correctly ordered) sentences are numbered 1 and 6. The rest of the passage is split into four parts and named B, C, D and E. These four parts are not given in the proper order. Choose the correct combination among the four alternatives given.

1. Aircraft such as balloons, nonrigid airships (blimps), and dirigibles are designed to contain within their structure a sufficient volume. B. When they are filled with a gas lighter than air (heated air, hydrogen, or helium), they displace the surrounding ambient air and float, just as a cork does on the water. C. Dirigibles are no longer in use, but they were lighter-than-air craft with a rigid internal structure, which was usually very large, D. It proved impossible to construct dirigibles of sufficient strength to withstand routine operation under all weather conditions. E. Balloons are not steerable and drift with the wind.
2. Most of them suffered disaster, either breaking up in a storm or through ignition of the hydrogen.