逻辑填空问题求助！！

我对逻辑部分的填空题总是很困惑，下面两个问题请g友们帮忙看一下:

1. A certain cultivated herb is one of a group of closely related plants that thrive in soil with high concentrations of metals that are toxic to most other plants. Agronomists studying the herb have discovered that it produces large amounts of histidine, an amino acid that, in test-tube solutions, renders these metals chemically inert. Possibly, therefore, the herb's high histidine production is what allows it to grow in metal-rich soils, a hypothesis that would gain support if ------

Answer: E

E. The concentration of histidine in the growing herb declines as the plant approches maturity.

Why is "E" the right answer, please? it doesnot make any sense to me.. (

2. Concerned about financial well-being of its elderly citizens, the government of R decided two years ago to increase by 20 percent the government-provided pension paid to all R--ers over 65. Inflation in the intervening period has been negligible, and the increase has been duly received by all eligible R--ers. Nevertheless, many of them are no better off financially than they were before the increase, in large part because -------

Answer: E

E. In R children typically supplement the income of elderly parents, but only by enough to provide them with a comfortable living.

Why is "E" the right answer, please again?? no sense except both of them got "E"

Thank you very much

anyone can help ??

第一个题题看懂了，答案没看懂，其他选项呢，因为herb have discovered that it produces large amounts of histidine, an amino acid that, in test-tube solutions, renders these metals chemically inert个原因，所以推出grow in metal-rich soils。问a hypothesis that would gain support if什么，E选项LZ是怎么理解的