Why did the huge animals like dinosour become extinct?

Explanation

Inspite of the fact that the cause for dinosaur extinction is still a mystery, following events could have played a role.
(i) Gas seeping and ash evolving from volcanoes suffocated most of the dinosaurs.
(ii) The entire population of dinosaur may have been wiped out due to diseases.
(iii) The dinosaurs could not survive after a big meteorite crashed into earth, drastically changing the climatic conditions.
(iv) Imbalances in food chain leads to starvationof the dinosaurs.