The apparent westward movement of a planet against the background of stars is called (1 point)
retrograde motion
revolution
rotation
universal gravitation

retrograde motion  

Explanation:

All the planets have direct motion or progade motion i.e. they move in eastward direction around the Sun. The exceptions are Venus and Uranus which apparently move westwards. This is type of motion is known as retrograde motion. Venus and Uranus move opposite to the other planets motion against the background of stars.

a. the law of proportion states the combination of 2 atoms in a specific ratio to produce multiple compounds such as the given statement of question ‘1st compound contains 88.8 % cu ’ indicates 88.8 g of cu is present along with 11.2 g oxygen in 100 g of compound whereas the statement ‘2st compound contains 79.9 % cu ’ indicates 79.9 g of cu is present along with 20.1 g oxygen in 100 g of compound

1st compound contains 88.8 g cu

for cu

m = 63 g /mol

atomic % = 88.8 /63 = 1.42

for o

m = 16 g /mol

atomic % = 11.2 /16 = 0.7

b. the emperical formula of 1st compound is

cu1.4o0.7

cu2o