The answer to your question would be C. Repetition.
Answer:
The agent probably knew about the murderer, because the accused only bought a ticket to return from the trip.
Explanation:
When the friend bought the travel tickets, he did not buy two tickets back, but only one, that is, he knew that his friend would not return, although he did buy two one-way tickets. Thus, this individual becomes the main suspect in the murder, since only the two friends were on the trip and it is necessary to investigate all the possibilities of his friend's death.
In this case, the police contacted the travel agent who passed all the ticket purchase information between the two friends.
Answer:
It would go in order the way it's put
Explanation:
The cause is that the interest in balloons grows so the first effect/cause would be that inventors develp hydrogen balloons, the second effect/cause is a balloon filled with hydrogen is launched, and the final effect is the very first hot air balloon is launched. I am sorry if this was confusing.