Heinrich did not propose any hypotheses. We only get a description of his experiment and the results.

His investigation confirmed prior observations (ravens indeed recruit others), but led to a radical reinterpretation (the reason ravens recruit others is not altruism, but self-interest; they need to group up to help access food belonging to older ravens).

We don’t get any theory proposed by Heinrich. If you consider “altruism” to be Heinrich’s theory, then (C) is wrong because Heinrich did not confirm that the ravens were altruistic.

We do not know what kinds of methods were used in earlier studies, or whether there were earlier studies. So we don’t know Heinrich used different methods.

We do not know whether there were previous studies or anything about the observational data in those studies. So we don’t know whether Heinrich replicated any studies or had a more limited set of data.