Question

the diameter of saturn is almost ten times that of the earth, but its density is much less. this can best be explained by the fact that saturn—
a is a gaseous planet
b is farther from the sun
c has a shorter period of rotation
d has a ring around its center

Explanation:

Saturn is a gas giant. Gases have lower density compared to the solid - rocky composition of Earth. Distance from the Sun (B) affects temperature and some atmospheric properties but not directly density in this context. Rotation period (C) relates to day - length and some dynamic processes but not density. The rings (D) are a separate feature and do not explain Saturn's overall low density.

Answer:

A. is a gaseous planet