Directions: There are 7 passages in this section. Each passage is followed by some questions or unfinished statements. For each of them there are four choices marked A, B, C, and D. You should decide on the best choice. 

Passage 6

The human brain contains 10 thousand million cells and each of these may have a thousand connections. Such enormous numbers used to discourage us and cause us to dismiss the possibility of making a machine with human— like ability, but now that we have grown used to moving forward at such a pace we can be less sure. Quite soon, in only 10 or 20 years perhaps, we will be able to assemble a machine as complex as the human brain, and if we can we will. It may then take us a long time to render it intelligent by loading in the right software or by altering the architecture but that too will happen. 

I think it certain that in decades, not centuries, machines of silicon will arise first to rival and then exceed their human ancestors. Once they exceed us they will be capable of their own design. In a real sense they will be able to reproduce themselves. Silicon will have ended carbon’ s long control. And we will no longer be able to claim ourselves to be the finest intelligence in the known universe. 

As the intelligence of robots increased to match that of humans and as their cost declines through economies of scale we may use them to expand our frontiers, first on each through their ability to withstand environments, harmful to ourselves. Thus, deserts may bloom and the ocean beds be mined. Further a head, by a combination of the great wealth this new age will bring and the technology it will provide, the construction of a vast, man-created world in space, home to thousands or millions of people, will be within our power.