To determine which inference would be invalid, let's analyze each option in relation to the likely context of the excerpt concerning mental health and societal attitudes towards the mentally insane.
A) People found it important to give the mentally insane a safe place to live.
- This could be valid, depending on the excerpt's discussion of care or shelter for the mentally ill.
B) The mentally insane were considered a danger to society.
- This might be a valid inference if the excerpt addresses societal views on the behavior or treatment of individuals deemed mentally insane.
C) People considered the mentally insane to be unable to determine their own status.
- This could also be valid if the excerpt discusses perceptions of competency in those labeled mentally ill.
D) Only someone who was medically qualified could declare someone mentally insane.
- This inference would generally be valid in discussions of mental health evaluations and legal definitions of insanity.
However, the validity of these inferences ultimately hinges on the specifics of the excerpt. If the excerpt does not provide evidence or context to support any of the claims, particularly regarding societal views or legal standards, a more careful examination is needed.
Among these options, if the excerpt does not discuss societal danger, personal autonomy, or legal definitions clearly, D could be the least likely to be inferred as it makes a strong claim about qualifications that may not be explicitly addressed.
Thus, based on the information provided, D) Only someone who was medically qualified could declare someone mentally insane stands out as an inference that may not be universally supported by most contexts addressing mental health discussions, especially in less formal situations or historical contexts.
In conclusion, the inference that is likely to be invalid without further supporting context would be option D.