Correct Answer: Constellation

Solution : The correct choice is the second option .

We know that a group of stars that forms a pattern and has a name is called a constellation .

The meanings of other given words are as follows:

• Horde : This means a large, unorganised group of individuals or a teeming crowd.
• Caravan : This means a group of people with animals or a large vehicle travelling together.
• Galaxy : This means any large system of stars or planets in space.

Therefore, among these options, the most suitable one-word substitute for the underlined group of words (a series of stars) would be constellation .