What is one characteristic of a sample of matter that indicates it is a pure substance?

a)it can be separated using by a physical means, such as filtering. b)the components in a pure substance do not have to be in definite ratios. c)if the composition of a sample varies, the sample is a pure substance. d)if the composition of a sample is fixed, the sample is a pure substance

D

Explanation:

If the composition of a sample is fixed, the sample is a pure substance. According to the law of definite proportions (constant composition), components of a pure substance must be in definite ratios regardless of the source.

i just calculated it all out, and not including weekends, and all the different days off. as of this school year (2018-2019) students are spending 2198 hours in school this year