How many moles of carbon are in the sample?

1 mole of carbon. Exactly 12 grams of pure carbon-12 powder is known as one mole. The number of atoms of carbon-12 present in this one mole sample is 6.022 136 7 x 1023. This number is known as Avogadro's number.

Idk the answer sorry

The density of water is 1 g/cm cubed and in order for the pebble to sink its density has to be greater than the density of water and in order for the twig to float its density has to be less than the density of water