Answer: A table or chair (or a lot of other furniture).

Answer: The feathers. A pound of feathers is measured in avoirdupois weight, in which one pound equals 16 ounces. Precious metals are measured in troy weight, in which one pound equals 12 ounces.

However, the ounces are not measured in the same way. In avoirdupois weight, one ounce = 437.5 grains. In troy weight, one ounce = 480 grains.

So, one pound of feathers weighs (16)x(437.5 grains) = 7,000 grains. One pound of gold weighs (12)x(480 grains) = 5,760 grains.

Answer: The gold weighs more.

In avoirdupois weight (feathers are measured in this way), one ounce = 437.5 grains. In troy weight (gold is measured in this way), one ounce = 480 grains.

Answer: Humanity.

Answer: The long dark cave is the barrel of a gun and the metal monster is a bullet.