4. There are other modes of travel … [section 4, line 1]
A. There are other means of travel
B. There are other ways of travel
5. In some countries ...; in others it is the opposite. [section 4, lines 2-4]
A. ... in others it is the contrary.
B. ... in others it is inversed.
6. … the degree of substitution ... [section 4, line 4]
A. how much substitution takes place
B. the kind of substitution that takes place