  Since 990 is divisible by ten, the answer is 990. If you were rounding off 994 the answer would also be 990. If you were rounding off 995, the answer would be 1,000.
Jupiter is the largest and most massive planet in the solar system. It was named after the chief Roman god. It is a gas giant composed of liquid and gaseous matter, and has many moons. Some of the storms in its atmosphere have lasted hundreds of years.
Thus, Jupiter's atmosphere is approximately 75% hydrogen and 24% helium by mass, with the remaining one percent of the mass consisting of other elements. The interior contains denser materials, such that the distribution is roughly 71% hydrogen, 24% helium, and 5% other elements by mass.