Explanation

• The sentence should read: "No one knows what color dinosaurs were because no sample of their skin has survived."
• کوئی نہیں جانتا ہے کہ ڈایناسور کیا رنگ تھے کیونکہ ان کی جلد کا کوئی نمونہ زندہ نہیں بچا ہے۔
• "Because" is a subordinating conjunction used to introduce a dependent clause that provides a reason or explanation for the main clause.
• In this case, the lack of surviving skin samples is the reason why we don't know the color of dinosaurs.