Although earthquakes often occur before a volcanic eruption, they are not the cause. The earthquakes are the result of magma (molten rock) moving underground leading up to an eruption. A few volcanic eruptions are thought to have been triggered or initiated by earthquakes, but this is not the typical case.
1/4. There is a 1/2 chance for each plant to pass on a gene for wrinkled seeds, and both must pass the gene, so we have 1/2*1/2=1/4.
