Ptolemy and copernicus were astronomers who had proposed theories about the solar system. ptolemy believed that the planets and the sun orbited earth. copernicus believed that earth and other planets circled a stationary sun. which of these statements best explains why ptolemy and copernicus made different observations about the solar system?

they studied outdated theories and evidences.
they had different backgrounds and interests.
they used incorrect methods of experimentation.
they made errors in their scientific calculations.

Achemistry student needs to standardize a fresh solution of sodium hydroxide. he carefully weighs out of oxalic acid , a diprotic acid that can be purchased inexpensively in high purity, and dissolves it in of distilled water. the student then titrates the oxalic acid solution with his sodium hydroxide solution. when the titration reaches the equivalence point, the student finds he has used of sodium hydroxide solution.calculate the molarity of the student's sodium hydroxide solution. be sure your answer has the correct number of significant digits.

Ab c or d ? i’m not sure what the answer is

What is the wavelength of a wave with a velocity of 50 m/s and a frequency of 5hz a 250 m b 0.1 m c 10m d 0.01 m