Answer:
My mom was so proud of me.
Explanation:
The original sentence is -
<em>My mom was so happy for me.</em>
Now, to add the word "proud" in the sentence, we cannot just put it in between any of the words or it will result in the formation of a new senseless sentence. And, in order for the word "proud" to be correctly used to make a meaningful sentence, we have to replace some word/ words. Also, the tense of the word "pride" is a noun or verb that cannot be really coordinated with the other words in the sentence. So, to make a meaningful sentence, the word 'pride' has to be changed into the adjective "proud'.
Thus, the final and new sentence will be-
My mom was so proud of me.
