The idiom "All that glitters is not gold" means that not everything that looks valuable or promising is actually so.
The correct sentence should be:
"All that glitters is not gold."
Thus, the correct answer is (A) "All that glitters is not gold."
Among scientists, the discovery of the double helix structure of DNA and the genetic code it incorporates is widely regarded to be one of the most significant scientific discovery of the twentieth century.