In the following passage, some words have been deleted. Fill in the blanks with the help of the alternatives given. Select the most appropriate option for each number.

A forest _______(1)_______ can be divided into three phases- Usually, grass and the dry undergrowth ignite first. This generates a ground fire, which is easy to _______(2)_______. If it grows into a wildfire, it can leap _______(3)_______ the treetops, especially in the case of conifers, leading to a crown or canopy fire where the flames spread rapidly. Crown fires are considerably more difficult to control and can easily grow into a _______(4)_______, which is practically impossible to _______(5)_______.