Question

question 19
which of the following was not observed by galileo?
stellar parallax
mountains & valleys in the moon
phases of venus
4 moons orbiting jupiter

Explanation:

Galileo observed mountains and valleys on the Moon, phases of Venus, and 4 moons orbiting Jupiter. Stellar parallax was not observed by him due to the limitations of his instruments and the vast distances involved.

Answer:

A. stellar parallax