The plural form of the word "goose" is geese.
The rewriting of the given sentence in the reported speech is "The speaker told us to be wary of "heard" which is a dreadful word".
The given words in the passive voice are: "I was five when I had mastered it".
This refers to the use of words that shows a speaker's words in subordinate clauses with the inclusion of a reporting verb.
Please note that some elements of this question are incomplete so I gave the answers which are complete.
Read more about reported speech here:
https://brainly.com/question/15886943