Select all that apply. chromosomes are rod shaped structures that contain dna are located in the nucleus occur in numbers that are the same for all members of a certain species occur in numbers that are the same for all organisms are organized into karyotypes for scientists to analyze

Select all that apply.
Chromosomes .
are rod shaped structures that contain DNA - this is mostly true but rather than "contain" DNA I would say they are composed of DNA. 
are located in the nucleus - yes, this is true. 
occur in numbers that are the same for all members of a certain species - this would be true as long as the organism is healthy. We do see chromosome mistakes that cause diseases such as Down Syndrome. 
occur in numbers that are the same for all organisms - no. Different species have different numbers of chromosomes. For example, humans have 46 and dogs have 78. 
are organized into karyotypes for scientists to analyze - yes, a karyotype is a way to organize and analyze chromosomes.