Choose the variant. 1) who is the tallest/tallest/taller student in your class? 2) the thames is as long/longer/the longer as the volga , isn't it? 3) you should be more attentive/ attentivelier/most attentive at the lessons. 4) travelling by plane is much more comfortable /most comfortable/much comfortable for me than travelling by bus.
2 as long as
3 more attentive
4 more comfortable