The rivers and lakes of the US from the basis of an easily constructible inland-water transportation system. If the railroads had not been developed in the first half ot he nineteenth century, a system of canals would have served as well. Coal and steel producation statistics for this period show that these industries alone would have provided a demand for transportation sufficient to justify a canal system, and the construction costs and freight rates recorded for canals of the nineteeth centruy would have allowed such a system to be economically feasible.

The author of the passage above has implicitly assumed which of the following.
a. Coal and steel production in the first half of the nineteenth century was not stimulated primarily by the demand for these products for railroad construction and operation.

b. Freight rates for canals in the first half of the nineteenth century were more economical than freight rates for railroads

c. Railrods and canals do not handle the same types of freight.

d. The construction of a canal requires less steel than the construction of a railroad, and the operation of a canal requires less coal than the operation of a railroad

e. The inland lakes and rivers in the US constituted natural barries to railroad construction in the first half of the nineteenth century.

This is Cause and Effect argument

author says The amount of steel and coal data indicates that canal system would had been a success.

The assumption is that steel and coal was not produced for railraod construction. If it was, the argument falls apart.

Hence A

I also vote A.

Other responses include ideas not discussed in paragraph such as freight rates, so these responses cant be assumed.