Final answer:
Substance p is likely neutral as indicated by methyl orange; q turned phenolphthalein colorless, suggesting it's acidic; r is neutral as it did not affect litmus paper; s behavior is inconclusive without clearer 'china indicator' information. The closest match, with an error, is option C.
Step-by-step explanation:
To determine which substances p, q, r, and s could be based on Aryaan's observations, we can evaluate each observation with our understanding of acid-base indicators:
- Methyl orange remains orange in substance p. This indicates that substance p is not strongly acidic or basic and is likely neutral.
- Substance q turned phenolphthalein colorless, which means that the substance is acidic, because phenolphthalein is colorless in acidic solutions.
- Substance r did not affect blue or red litmus paper, suggesting that substance r is also neutral.
- Finally, substance s turned china indicator green. This may refer to a 'universal indicator', where green typically indicates a neutral pH. However, because there is no standard 'china indicator' and the observations for substances p and r already suggest neutrality, it's possible that s may reflect a slightly acidic or basic nature, but the given information is inconclusive for s.
Considering these results, the most likely identities for p, q, r, and s based on the provided observations are:
- p = neutral
- q = acidic
- r = neutral
- s = neutral (with the caveat that we cannot be certain without more information on 'china indicator')
Therefore, the closest match from the provided options is C) p = neutral, q = base, r = acid, s = base. This seems to contain a typographical error, as observations for q indicate acidity, not basicity. With this discrepancy noted, none of the options perfectly match the observations, so we advise that Aryaan consults the source of the 'china indicator' for clarity on substance s.