Galileo's three most important discoveries were? list and explain them

 The three important discoveries of Galileo are:
1) Telescope
2)Milky way
3)Thermoscope

Thermoscope: It is the earlier version of thermometer for measuring the temperature discovered in the 16th century.

Telescope: It was invented to view far away objects like trees, birds etc and the celestial objects.

Milky way Galaxy: He discovered the milky way galaxy that contains our solar system.

Then the answer would be d then