Which of these is the main role of the president of the united states?

a.
to make the nation’s laws
c.
to decide a law’s constitutionality
b.
to carry out the nation’s laws
d.
to interpret the constitution

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.