Why is it difficult to observe individual chromosomes with a light microscope during interphase?
a) the dna has not been replicated yet.
b) the spindle must move them to the metaphase plate before they become visible.
c) they leave the nucleus and are dispersed to other parts of the cell.
d) sister chromatids do not pair up until division starts.
e) they have uncoiled to form long, thin strands.

They have uncoiled to form long, thin strands.

Explanation:

Chromosomes are present in cell nucleus and consist of chromatin. Genes are present in linear order on chromosomes.  The chromosomes become visible under the microscope as distinct structures during cell division. When cells are not dividing, the chromosomes decondense to loose their individuality and make the mass of chromatin.  

Chromatin is complex of DNA and packing proteins. As the cells enter the prophase stage of cell division, condensation of chromatin occurs and individual chromosomes become visible under microscope. Before that (during interphase), chromosomes are not visible as they are present in decondensed form.

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