Bonjour,
4 - Many people think it is (+ dangerous) to fly than to take a train.
Many people think it is more dangerous to fly than to take a train.
( Beaucoup de gens pensent qu'il est plus dangereux de prendre l'avion que
de prendre un train.
comparatif de supériorité. "dangerous adjectif long = more dangerous
5 - Trains are (-polluting) than planes and they are not (= noisy)
Trains are less polluting than planes and they are not as noisy
( Les trains sont moins polluants que les avions et ils ne sont pas aussi
bruyants )
comparatif d'infériorité "polluting" adjectif long = less polluting
comparatif d'égalité = as + adjectif = as noisy
; )