Answer:
Governing politics!
Step-by-step explanation:
General Yahya held Pure Elections which resulted in victory of Mujeeb ur RAHMAN, so according to the rule, Mujeeb should be the next Prime Minister of Pakistan. Bhutto became angry at his defeat and boycotted the Assembly.
Yahya(Former President of Pk) sided with Bhutto.
Note; Bhutto won the votes with a high rate in West Pakistan while Mujeeb clean swipe votes in East Pakistan.
Also, 1 cause was the National Language of Pakistan.
Quaid e Azam declared Urdu as National Language while Bangladesh's want Bangali as the National Language.
(Btw sorry for my bad English!)
{Correct me if I'm wrong}