Thus a watchful grazing annimal will see the slight movemnt that betray the presnece of a predator  long before it's close enough to launch an attack.

请问老师to launch an attack.是不定式做目的状语吗？ 可以enough to一般不都是结果状语吗？He has never managed to get enough money to have the church clock repaired.这句话呢？