<u>Answer:</u>
Ptolemy accounted for 'retrograde motion' in his model of the solar system by introducing smaller circles named 'epicycles'.
<u>Explanation:</u>
- According to Ptolemy, the Sun and the other planets in the Solar system orbited around the Earth.
- The Greeks were convinced that Ptolemy's earlier model did not provide for backward or the retrograde motion.
- Ptolemy thought over it for a while and theorized the possibility of 'epicycles'.
- According to Ptolemy, the planets that orbited Earth also orbited another smaller point.
- The smaller orbits followed by the planets while in motion around the Earth in a larger orbit were introduced by Ptolemy as 'epicycles'.
- Until Kepler proposed his models of the functioning of the Solar system, Ptolemy's models were considered the most relevant.
The answer is D, both are 12
Answer:
Silicate-Oxygen tetrahedro
Explanation:
Silicate-Oxygen tetrahedro are the most abundant and basic structure of common minerals.
These are silicate minerals which formed to silicate rock forming mineral. These constitute about 90% of earth crust. Silica SiO2 consider as most common mineral on the surface of earth also known as Quartz. The the most andundant element in the earth crust is oxygen, mainly found in combine form.
