what most likely caused the ice - ages?\no the size of tree rings and the amount of pollen grains\no solar…

Brief Explanations:

The tilt of the Earth's axis (obliquity) and the shape of its orbit (eccentricity) are major factors in the Milankovitch cycles which are thought to be a primary cause of ice - ages. Tree rings and pollen grains are used to study past climates but don't cause ice - ages. Solar flares and ejections have short - term effects on Earth's magnetic field and upper atmosphere, not long - term ice - age cycles. The temperatures of the Sun and Moon don't directly cause ice - ages; the Sun's overall energy output has a more general impact on Earth's climate but the tilt and orbit are key for ice - age cycles.

Answer:

the tilt of the Earth's axis and the shape of its orbit