What is the relationship between negative and positive externality?

A negative externality exists when a cost spills over to a third party. A positive externality exists when a benefit spills over to a third-party. Government can discourage negative externalities by taxing goods and services that generate spillover costs.

is there answer choices?

giant impact theory - the moon was formed from the collision between earth and another mars-sized body.

colliding planetesimals hypothesis - the moon was formed from the same cloud of material as earth.

capture hypothesis - the moon was locked into orbit by earths gravity as it was passing by it.

accretion hypothesis - the moon was formed from collisions and combining of planetesimals.

i think this is right, if not and you know better let me know.