Is it informal letter or formal letter
Answer: They drew his chariot when Achilles left home for the Trojan War.
Explanation:
The horses, who were immortal, were given by Poseidon as a gift to Achilles's father Peleus upon his wedding to the goddess Thetis: magnificent racing stallions, gifts of the gods to Peleus, shining immortal gifts. Peleus then gave the horses to Achilles to draw his chariot when his son left home for the Trojan War.
It is what number. It is the proper way to say it.
Plethora would be the collective noun because it is a group.