Final answer:
The largest sector of the population by language is Spanish speakers, considering both the United States demographics and global language statistics.
Step-by-step explanation:
The largest sector of the population by language is Spanish speakers (D). This is supported by data indicating that a significant portion of the United States speaks Spanish at home and by worldwide figures showing a large proportion of native Spanish speakers.
Although Brazil has a notable Japanese population and there is a substantial number of German Americans, the information regarding language speakers and ethnic backgrounds highlights that Spanish speakers comprise a larger sector globally. Moreover, the increase in Hispanic populations in the United States further underscores the prominence of Spanish speakers.
In the United States, there is a notable trend of growing minority populations, especially among Hispanics which contribute to the growing number of Spanish speakers. Additionally, the historical context of German Americans as a large ethnic group, mainly assimilated now, still shows that the Spanish-speaking sector surpasses this in size due to broader global presence.