To be valid a scientific observation needs

Which element is used in photosynthesis found in atmosphere and fixed by bacteria?

Dna has unique properties that allow it to accurately retain genetic information, even after multiple rounds of replication. one aspect of dna that allows it to accurately store genetic information is the base pairing from chargaff\'s first rule of the four nucleotide bases. if the c content of a dna molecule is 22%, what are the percentages of the remaining bases?

Melting glaciers is a serious threat to the environment what is the possible consequence of melting glaciers on polar bears?