I'm having problems with this:

Question

Compare the trajectory of a planet and a comet.

Answer 1

Planet is usually a pretty round elliptical orbit, often almost circular, around a star.
A comet may go entirely beyond the planets and then come close to the sun again. The orbit is likely to be a skinny (highly eccentric) ellipse with the focus at the sun far from the other focus of the ellipse.

Answer 2

i don't really know how to balance a reaction 2C2H2(g)----> fCO2(g)+______?