Congress supported construction of the transcontinental railroad by
a. paying the costs of construction.
b. providing loans and land grants.
c. paying for the development of faster steam engines.
d. bringing laborers from china to work for low wages.

Congress supported construction of the transcontinental railroad by B. providing loans and land grants. This construstion refers to the Civil War event during which Pacific Railroad Acts of 1862 and 1864 constructed the lines.

productive most commonly means: achieving or producing a significant amount or result.

explanation:

productive can also mean:

producing or giving rise torelating to or engaged in the production of goods, crops, or other commodities.

these depend on how the word productive is used. most likely productive will mean   achieving or producing a significant amount or result.

Ibelieve its c not quite sure.