Bilingual children_________________________ disadvantaged in the past.

The correct choice effectively conveys the idea that there is an ongoing perception regarding bilingual children and their status in the past. The phrase "are thought to have been" indicates a current belief or opinion about a past condition, and it implies that this perception is still relevant today.

In this case, "are thought to have been" communicates that people currently hold the view that bilingual children faced disadvantages in previous times, which connects the present belief with a notion about the past. This option maintains a sense of continuity and relevance between current thinking and historical context.

Other choices do differ in subtle yet important ways. For instance, "were believed to have been" implies that the belief is outdated or not current, which shifts the focus away from present beliefs. "Had been seen as" suggests a definitiveness to the past perspective but lacks the present relevance seen in the correct answer. Lastly, "are considered to have been" is similar in structure but typically suggests a more formal and possibly authoritative judgment, which might not align with the more subjective tone set by "thought."

Overall, the chosen option effectively maintains the relationship between present attitudes and their historical context regarding the perception of bilingual children.