The conclusion is that a developer who wishes to make a large profit would be wise to buy
urban waterfront lots and erect residential buildings on them. The basis for that claim is that people pay large sums for beach front homes. We are asked to strengthen this argument.
(A) This choice states that people have more buying power today than in previous centuries. This does not strengthen the claim that a developer will make money on urban waterfront properties.
(B) CORRECT. This choice states that homeowners will be willing to spend large sums of money on residential properties in traditionally industrial or commercial districts. Since we know from the argument that urban waterfronts have traditionally been industrial, this fact strengthens the claim that a developer can make a profit on urban waterfront properties.
(C) This choice states that many urban waterfront lots are available for purchase. This does not suggest, however, that a developer will be able to sell them after he or she builds on them.
(D) This choice states that many coastal cities are giving tax breaks to developers who rehabilitate the waterfront. But this does not suggest that anyone will buy the developed properties.
(E) This choice states that properties in the interior of cities are more expensive than those on the waterfront. Although waterfront properties are therefore cheaper to acquire, this does not necessarily mean that a developer can make a profit after buying such properties.