Which sentence uses "too" correctly?

Question

The monarch butterfly population is facing numerous challenges too their survival and adaptation.
The monarch butterfly population has declined drastically, affecting the ecosystems it is native too.
Efforts too protect the monarch butterflies must be taken, as they are important members of the food chain.
Too many factors have contributed to the declining monarch butterfly population, from habitat loss to climate change.

Answer 1

Too many factors have contributed to the declining monarch butterfly population, from habitat loss to climate change.