Not necessary, because we already know that whales behave in unusual ways around divers or submarines. Whether that behavior is aggressive or nonaggressive doesn’t affect the biologists’ reasoning.

Necessary, because if it were not true — if the behavior of sea lions under human command will NOT be within the range of behavior the whales are used to — then we cannot be confident that the whales won’t behave unusually, just as they do when divers or submarines attempt to observe them. In other words, (B) is necessary because the biologists must think the human-commanded sea lions won’t be considered “novel stimuli” to the whales.

Not necessary, because even if the sea lions are aware of their cameras, we have no reason to think that would affect how whales react to the sea lions.

Not necessary, because the issue is whether the whales will behave unusually around the sea lions. The author thinks sea lions will allow us to study whales, not because sea lions can film much more closely than divers, but because sea lions won’t lead to unusual behavior.

The issue is not what whales prefer; the issue whether whales will behavior unusually around sea lions. Even if whales prefer divers or submarines over sea lions, that doesn’t tell us anything about whether the whales might behave unusually around sea lions.