We have no reason to think the author believes parathion should be used if predators don’t work. Parathion doesn’t kill C-mites; it kills T-mites.

Not supported, because we have no reason to think the author cares about the effects of predators on other kinds of insects. What matters is whether the predators can kill cyclamen mites.

Supported, because we know that parathion would do “far more harm than good.” So it would make sense to use it only if we can’t use Typhlodromus mites to control cyclamen mites. You might be uncomfortable with “only if” or the reference to “insecticides” instead of “parathion,” but there’s no better answer. No other answer has any amount of support.

Not supported, because we don’t know whether the author would prefer a pesticide that kills both pests and predators over use of predators. We know she’d prefer use of predators over a pesticide that kills only predators, but that doesn’t tell us about her preference concerning a pesticide that kills both predators and prey.

Not supported, because we don’t know whether predators generally don’t harm the crops that their prey feed on. The author never tells us whether they can harm the crops. In addition, even if you think there’s support for the claim that predators generally don’t harm the crops, this isn’t one of the things the author identifies as contributing to the effectiveness of T-mites in P2. So we have no reason to think the lack of harm to crops contributes to predators’ effectiveness.