Asteroids This is a matter of knowing the definitions. Although the biggest hint is "Make up a belt between Mars and Jupiter" which should cause you to immediately think "Asteroid Belt". But let's look at the options and see what fits.
Comets - Mostly comprised of ice and dust. They're not "rocky", so this isn't a good choice.
Asteroids - Nothing the lecture describes conflicts with what an asteroid is, so this is the correct choice.
Meteor - Key thing here is a meteor is that a meteor is a small body that's burning up in the Earth's atmosphere, causing a streak of light. And that's not what the lecture is describing, so this is a bad choice.
Meteoroids - This is a body orbiting the sun, that will in the future become a meteor. And that's not something in a stable orbit between Mars and Jupiter. So this is also a bad choice.
C6H12O6 = 12 x 6 + 1 x 12 + 16 x 6 => 180 g/mol
You can extract the iron fillings from the sand by using a magnet
Oxygen is a pure substance, as it is composed of only a single kind of atom. Which is the oxygen atom, it cannot be broken or degraded down any further into constituents that make up the element. In terms of both chemically and physically.