I am very confused when dealing with questions where verb forms serves as modifiers.
Most of the time i am unable to find the the part that is being modified by modifier.

Ex: from power score sentence correction bible given below

For the stegosaurus, a dinosaur from the late Jurassic period, the seventeen bony plates embeddded in its back we're necessary elements for survival, to regulate its temperature throughout its body and to protect it from other carnivores.

It's written that the infinitives 'to regulate' and 'to protect ' have nothing to modify.

Can someone help me get the concept.

Thanks,