Theory:

     The python, who had been quietly following Golu, came to the bank and said, “If you do not pull as hard as you can, the crocodile will drag you into the stream.”
 
     Golu sat back on his little haunches and pulled and pulled. The crocodile slipped into the water making it all creamy with great sweeps of his tail, and he also pulled and pulled.
 
     Then the python coiled himself round Golu’s stomach and said, “Let’s pull harder.” Golu dug in all his four legs in the mud and pulled. The nose kept on stretching. At each pull the nose grew longer and longer and it hurt Golu. The nose was now five feet long, but it was free at last.
Explanation:
 
Suddenly, the python that Golu had previously encountered reappeared on the scene. Since the time Golu left after wishing it (the python) farewell, it seemed to have been following Golu. It (the python) then moved down to the riverbed and helped Golu. It (the python) warned Golu that the crocodile would take him into the stream if he didn't pull as hard as he could.
 
Golu pulled hard on his haunches, and the crocodile dragged him even harder. With a great sweep of its tail, the crocodile rushed into the water and continued to drag Golu with considerable effort. For a long time, Golu and the crocodile were pulling each other.
 
The python ultimately wrapped itself around Golu's stomach, allowing him to pull even harder. Though the python's assistance had little or no effect, it gave Golu more confidence in knowing that he had someone behind him to encourage him. Then Golu dug all four legs into the mud and pulled.
 
However, Golu's nose kept extending further and longer as he pulled, causing him pain. Golu could finally escape the crocodile's onslaught, but his nose grew to be five feet long.
 
Golu's expanded nose.jpg
Golu's expanded nose
 
Meaning of difficult words:
 
S.No
Words
Meaning
1.
TugRepeatedly pulling something hard
2.
SweepTo push or move someone or something suddenly with a lot of force
3.
OnslaughtAn attack that is forceful or powerful
Reference:
National Council of Educational Research and Training (2007). Supplementary. Golu Grows a Nose – Rudyard Kipling (pp.30-34). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.