Answer: mongooses, bluffs, knives
Explanation:
In most of the cases to make a regular noun plural you just write an -s at the end of the singular noun. This is the case of BLUFF-BLUFFS.
However, there are some exceptions. For example, in the case of the nouns that end in F or FE you change it to VES. For example, KNIFE-KNIVES.
If the noun finishes in S as in the case of MONGOOS you add an ES at the end to make it plural, just like this MONGOOSES.
