According to boyle’s law, when the pressure on a gas increases at constant temperature, its volume
a. increases.
b. stays constant.
c. decreases.
d. increases, then decreases

The correct answer would be C. Decreases.
PV = k
Where P is pressure of the gas and V is volume of the gas and k is constant.
It easily derived by the equation above.
Boyle’s law states that when the gas amount and its temperature the same or held constant, within a closed system, the relation of the pressure exerted by the gas is inversely proportional to its volume. So in the situation, the pressure increases, so its volume decreases.

Neptune is the eighth planet from the sun. it was the first planet to get its existence predicted by  mathematical calculations  before it was actually seen through a telescope on sept. 23, 1846. irregularities in the orbit of  uranus  led french astronomer alexis bouvard to suggest that the gravitational pull from another celestial body might be responsible. german astronomer johann galle then relied on subsequent calculations to   spot neptune via telescope. previously, astronomer galileo galilei sketched the planet, but he mistook it for a star due to its slow motion. in accordance with all the other planets seen in the sky, this new world was given a name from greek and roman mythology — neptune, the roman god of the sea.