Which model of the solar system best supports retrograde motion of the planets?

a. ptolemy's model

b. the geocentric model

c. the heliocentric model

d. an earth-centered model

Ais useful when you need a simple machine to you separate two things. a. lever b. screw c. pulley d. wedge

This is for my 8th grade science class, i really don’t understand. can someone me? , lol.

When can a theory be modified if a new type of technology allows for new observations that raise new questions? a-immediately, while the questions about the theory are being asked b-after new hypotheses related to the theory are tested in experiments c-only after the new observations disprove all parts of the theory d-while scientists begin to think about how the theory could improve