Answer:
A horse raced down Emma's street, another one followed it.
In this sentence, another is the single word as it shows the connection between the first sentence and the latter part of the sentence.
Because William had lost his wallet, his friend bought his lunch.
In this sentence, because is the single word as it shows the outcomes that happen when William loses his wallet.
Both of the kittens grew up to be large, orange cats.
'Both' is the single word here as it is showing relationship between ideas.
