Why was Giuseppe Mazzini considered the heart of Italian unification?

Which factor has played the most important role in changing the way history is studied over time?

How would lincoln's assassination change the direction of reconstruction? the radicals used this opportunity to take control of the plans. the south refused to cooperate with any plans after lincoln his death would put an end to all reconstruction plans. lincoln was too weak to carry out his plan and now it could be carried out.

What important discovery was made by edmond halley and alexis clairaut, using newton's ideas of mathematics and gravity? they created the scientific method to outline how science should be conducted. they were able to find the orbit of a comet and predict the year of its return. they discovered the three newest planets--uranus, neptune, and pluto. they explained why objects appear to have color.