What must occur for air masses to form fronts?

they must increase in strength.
they must collide with each other.
they must move from west to east.
they must create air-pressure differences.

Which of these is the sound of fish slapping against human flesh?

Which modern technology has not made a great difference in the inuit way of life?

Which statements describe sustainable development? multiple answer choice -fishing does not remove more fish from water systems than can be replaced by the number of fish that will be born to replace them. -sustainable development is development that is designed to improve the economic conditions in less-developed countries. -sustainable development is mainly a regional issue. -sustainable development means water is used at a rate that won't reduce the amount available for future use. - sustainable development policies only need to be concerned with environmental protection. - trees cannot be cut down faster than the number that will be replaced by new growth.