They're going by ......
taxi
Are they going by car or on foot?
They're going on foot
Are they going by plane or by helicopter?
They're going by plane
What's this?
It's a lorry
What's this?
It's a hot-air balloon
What's this?
It's a helicopter
Are they going by lorry?
No, they aren't
How do you go to school?
I go to school on foot/I go to school by car
Are they going by motorbike?
Yes, they are
They're going by .....
train
Are they going by boat?
Yes, they are
Is she going by bike?
Yes, she is
Is this a bike or a tandem?
It's a tandem
Do you go to school on foot?
Yes, I do/No, I don't