Answer:
The correct order of the sentence is:
I cannot imagine how happy he was after receiving the results
Step-by-step explanation:
The grammatical structure that helps to organize this sentence correctly is " embedded questions". This structure follows the pattern : introductory phrase + question word + embedded question (subject + verb).
introductory phrase: I cannot imagine
question word: how happy
embedded question: he was after receiving the results.
These words can get organized in a propper form as long as we know what part of speech represents each one of them.