Uzupełnij zdanie wstawiając jedno słowo w każde puste miejsce.

a) .......... longer the journey, ........ more supplies travellers had to take.
b) Hundreds of years ago, travelling by sea was ......... quicker ........ trying to make the same journey overland
c) The guitar isn't ........... difficult to play as many other instruments which is why it is one of the .......... popular to learn.