Last term our maths teacher set so difficult anexamination problem ______none of us worked out

For a long time, he hesitated whether he should tell us ____ what had happened

下列词语中加横线字的注音全都正确的一项是（ ）

You buy the fruits, ________ I’ll cook breakfast.[ ]

.Urban crowdedness would be greatly relieved if fares________on public transport were more reasonable.