大全-Ⅰ-3.
Economies in which a high percentage of resources are invested in research and development show greater growth in the long run than do those in which resources are channeled into consumption. Japanese workers spend a higher percentage of their income investing in research and development than do American workers.

Which of the following, if true, tends to weaken the argument?

(B) Class mobility, highly valued in American culture, is encouraged by a growing rather than a stagnant economy.

(C) Studies have shown that countries with high consumption rates prosper in the short run.

(D) Proposed changes to the tax code could involve strict limits on the deduct ability of interest, and increased allowance for research.（E）

(E) Because a decreasing percentage of the United States is under 40, an age when savings are traditionally low, the savings rate will increase without changes to the tax code.

答案是E, 没有问题,  但画线部分是什么意思呢?  为什么percentage ....... is under 40, an age, 后面又来个an age..