Why should the percentage of allowed weed or other crop seed be under 2 percent? O These other plants will compete with the desired plant for attention, rain, and desiccants.
O These other plants will compete with the desired plant for light, space, and nutrients.
O These other plants will compete with the desired plant for shelf space, threshing, and roguing.
O These other plants will compete with the desired plant for soil, worms, and warmth.

vote read

explanation:

plate tectonics and volcanic euptions

over time, plate tectonic processes cause continents to move to different positions on the globe.

for example, britain was near to the equator 300 million years ago, and therefore was hotter than it is today. for further details look at our climate through time poster or online map.

the movement of the plates also causes volcanoes and mountains to form and these too can contribute to a change in climate.

mountain ranges formed by plate tectonics. large mountain chains can influence the circulation of air around the globe, and consequently influence the climate.   warm air might be deflected somewhere cooler by the mountains.

"d.) carbon dioxide and hydrogen sulfide"